This is going to be a bit long but I tried to make it as easy to follow as possible, the information on the wiki is minimal on this topic and it took me a bit to understand where every value fits in when calculating final prices. I color coded the variables or settings so that you can follow each value and where it goes or where it will end up being a little bit easier.
Initial price calculations:
I wanted to understand how the settings I change in my mod impact Fallout 4 prices, and as everyone probably does the first place I checked was Fallout 4 wiki entry for Charisma and its effect on Barter.
However, the wiki only has the following formulas for buying and selling price 'modifiers':
BUYING PRICE MODIFIER = 3.5 - (CHARISMA * 0.15)
SELLING PRICE MODIFIER = 1 / BUYING PRICE MODIFIER
Are those initial prices? final prices? they say 'modifier' so what exactly are they modifying and how? I went digging through old wikis, old mods, old reddit threads, etc etc. and after several days I ended up finding some actual useful information here in the UESP wiki so and I sat down to try to make sense of it all and see how those formulas are used in Fallout 4 since FO4 doesn't have a Speech skill as Skyrim does, nor a Barter skill as previous Fallout games had, but it does have CHARISMA wedged into its formulas as the wiki suggests so there had to be some correlation between that and fBarter game settings (plus, it's Bethesda, they've been using roughly the same formulas for more than a decade, with slight tweaks).
To understand how the FO4 wiki and UESP wiki formulas are correlated there are a few (global) game settings that start with fBarter in their names that we need to know about, they are used by the game to modify both buy and sell prices in the game, and I was interested in fBarterMax and fBarterMin in particular since I've seen mods over the years change them but none of the authors provided any information on how they might actually apply to the final prices (or if they did, the explanations were pretty minimal and didn't explain the full picture).
These are the vanilla values for those game settings:
- fBarterMax vanilla value = 3.5
- fBarterMin vanilla value = 2.0
These two settings define both:
- A base vendor-selling-range (in vanilla this range is 200% to 350% of an item's base value).
- A base vendor-buying-range (in vanilla this range is 30% to 50% of an item's base value).
Notice that both settings are used for both calculations, so any change to either of them will affect both the selling AND buying ranges.
After looking at the BUYING PRICE MODIFIER formula in the wiki I realized those numbers came from applying the same Skyrim prices formula only with a tweak to accomodate CHARISMA into it:
BASE PRICE FACTOR = fBarterMax - (fBarterMax - fBarterMin) * (CHARISMA/10)
BASE PRICE FACTOR = 3.5 - (3.5 - 2.0) * (CHARISMA/10)
BASE PRICE FACTOR = 3.5 - (1.5) * (CHARISMA/10)
BASE PRICE FACTOR = 3.5 - (CHARISMA * 1.5) / 10
BASE PRICE FACTOR = 3.5 - CHARISMA * 0.15
So what FO4 wiki is calling BUYING PRICE MODIFIER is actually what UESP wiki calls PRICE FACTOR which I renamed to BASE PRICE FACTOR to clarify that it's still a formula that's calculating the 'initial' price of an item, hence why the FO4 wiki puts it as a 'modifier', because it will end up modifying the final price calculation.
Ok so now I understand why the wiki has those formulas, that BASE PRICE FACTOR = BUYING PRICE MODIFIER, and how fBarterMax and fBarterMin impact the base price factor calculation.
Buy and Sell prices modifiers (mutipliers):
Since Fallout 4 doesn't have an actual Barter skill you can increase like in previous Fallout games by spending points when you level up (the Speech Bobblehead only adds 100 to vendors by the way so it doesn't affect prices directly), I ended up checking in the Creation Kit how the following things work since these perks and items are the ones tightly related to buying/selling prices:
- Cap Collector perk ranks 1 and 2
- Barter Bobblehead
- Junktown Vendor magazines
- Grape Mentats
Other items like some alcohol and Charisma-boosting clothing/armor just modify CHARISMA so those are easier to understand, they just increase or decrease CHA stat.
The majority of those perks and items modify prices by applying a multiplier to modify the final price. Here's a list of the multipliers each of them apply (some are multiplicative, others additive):
Cap Collector rank 1 (10% better prices):
- Mod Buy Prices multiplier = 0.90
- Mod Sell Prices multiplier = 1.10
Cap Collector rank 2 (20% better prices, stacks multiplicatively with rank 1):
- Mod Buy Prices multiplier = 0.80
- Mod Sell Prices multiplier = 1.20
The effects of Cap Collector rank 2 stack multiplicatively with rank 1 for a total of 32% better selling prices (1.10 * 1.20 = 1.32), and a total of 28% better buying prices (0.90 * 0.80 = 0.72, which means prices will be 72% of what they should have been, or in other words it's 28% better). Keep in mind these are still 'modifiers' to the final price calculation.
Cap Collector rank 3:
- Rank 3 doesn't really modify either buy/sell multiplier, this rank just injects 500 caps to vendors but I added it here to be thorough with my investigation.
Barter Bobblehead (5% better prices):
- Mod Buy Prices multiplier = 0.95
- Mod Sell Prices multiplier = 1.05
Junktown Vendor (3% better prices, stacks additively):
- Mod Buy Prices multiplier = 0.97 (rank 1), 0.94 (rank 2), 0.91 (rank 3), 0.88 (rank 4), 0.85 (rank 5), 0.82 (rank 6), 0.79 (rank 7), 0.76 (rank 8)
- Mod Sell Prices multiplier = doesn't apply, these magazines only benefit buying prices.
Grape Mentats (by themselves they act in every way like having +5 CHARISMA and having Cap Collector rank 1):
- These mentats effectively give you +5 CHA for the purposes of calculating prices.
- Mod Buy Prices multiplier = 0.90
- Mod Sell Prices multiplier = 1.10
What's the point of all of this? The point here is that the FINAL BUY PRICE or FINAL SELL PRICE are influenced by all those modifiers (usually multipliers).
So what ARE the final buy and final sell prices formulas then?
To calculate final buy or final sell prices the game uses the following formulas:
FINAL BUY PRICE = base value of an item * Mod Buy Prices multipliers * BASE PRICE FACTOR
FINAL SELL PRICE = (base value of an item * Mod Sell Prices multipliers) / BASE PRICE FACTOR
Notice that both formulas are using the same 'BASE PRICE FACTOR', this is because the first one is multiplying by it (so it's applying the BUYING PRICE MODIFIER directly) and the second one is dividing by it (so it's dividing by (1 / BUYING PRICE MODIFIER) which was the SELLING PRICE MODIFIER, so in the FINAL SELL PRICE formula it's just easier to divide by BASE PRICE FACTOR directly, this way we use the same price factor instead of having to use the SELLING PRICE MODIFIER to make the math more troublesome to follow.
Understanding vanilla barter PRICE RANGES, where do they come from?
If we apply zero CHARISMA or 10 CHARISMA to the formulas we've seen so far, we can have the base vendor buying and selling ranges I mentioned at the beginning (200% to 350% of an item's base value for selling, and 30% to 50% of an item's base value for buying).
Note that:
- Mod Buy Prices multipliers and Mod Sell Prices multipliers are rounded to two decimal places (a percentile), unrounded (untruncated) values shouldn't be used as they will yield incorrect results (I've checked this and the Skyrim wiki is correct, the results and slightly off if you do that).
- The FINAL BUY PRICE and FINAL SELL PRICE are also rounded to the nearest whole number to get the *actual* final prices.
At 0 CHARISMA and no perks:
The BUYING PRICE MODIFIER is 3.5 for buying, and the SELLING PRICE MODIFIER is 0.285 for selling (actually it would be 0.30 for selling because it's rounded to nearest two decimals):
- This means the FINAL BUY PRICE for an item that costs 1 cap is going to be (1 * 1 * 3.5) = 3.5, and if you want it in percentile: 3.5 * 100 = 350% (so the price to buy items from a Vendor at 0 Charisma is 350% the item's real value).
- For the FINAL SELL PRICE we use the same BUYING PRICE MODIFIER but we divide by it, in this case it would be (1 * 1 / 3.5) = 0.285 (or 0.3 rounded), and if you want it in percentile: 0.3 * 100 = 30% (so the price to sell items to a Vendor at 0 Charisma is 30% the item's real value).
At 10 CHARISMA and no perks
The BUYING PRICE MODIFIER is 2 for buying, and the SELLING PRICE MODIFIER is 0.500 for selling.
- This means the FINAL BUY PRICE for an item that costs 1 cap is going to be (1 * 1 * 2) = 2.0, and if you want the percentile: 2.0 * 100 = 200% (so the price to buy items from a Vendor at 10 Charisma is 200% the item's real value).
- The FINAL SELL PRICE in this case would be (1 * 1 / 2.0) = 0.5, and if you want the percentile: 0.5 * 100 = 50% (so the price to sell items to a Vendor at 10 Charisma is 50% the item's real value).
So here we can see that at the beginning of the article when I mentioned the vanilla base vendor-selling-range as being 200% to 350% of an item's base value, the 200% actually applies for when you have 10 CHA, and 350% for when you have 0 CHA. On the other hand, the vanilla base vendor-buying-range is 30% to 50% of an item's base value, but in this case 30% refers to the amount of money a vendor will pay you when you have 0 CHA and 50% will be your best (vanilla) selling price to them at 10 CHA.
Understanding vanilla barter PRICE LIMITS, why do they exist?
The examples I wrote above explain what type of prices you would get with 0 CHARISMA and go up to 10 CHARISMA at which point the best prices you should be able to get are: selling your stuff at 50% the item's base value, and buying stuff from vendors at 200% the item's base value, but obviously there are ways to have higher than 10 CHARISMA in the game. The following table (taken from the wiki) shows the BUYING PRICE MODIFIERS and SELLING PRICE MODIFIERS for having 0 CHARISMA to 16+ CHARISMA which is achievable with perks, items and buffs.
CHARISMABUYING PRICE MODIFIERSELLING PRICE MODIFIER
0 3.50 0.2857
1 3.35 0.2985
2 3.20 0.3125
3 3.05 0.3279
4 2.90 0.3448
5 2.75 0.3636
6 2.60 0.3846
7 2.45 0.4082
8 2.30 0.4348
9 2.15 0.4651
10 2.00 0.5000
11 1.85 0.5405
12 1.70 0.5882
13 1.55 0.6452
14 1.40 0.7143
15 1.25 0.8000
16+ 1.20* 0.8000*
The table stops at 16 because there is an actually limit to how low vendors prices can get when selling items to you, or how high vendors prices can get when buying items from you (*while the numerical results for BUYING PRICE MODIFIER and SELLING PRICE MODIFIER specifically in the case of 16 would be 1.10 and 0.90 respectively, the game applies the 1.20 and 0.80 caps indicated below to both).
These limits are set by two other global game settings the game has that I didn't mention at the beginning called:
- fBarterBuyMax (vanilla value is 1.20)
- fBarterSellMax (vanilla value is 0.80)
These two settings are caps Bethesda added to limit the BUYING PRICE MODIFIER and SELLING PRICE MODIFIER values, if one gets a buying modifier that is less than 1.2, the game will use 1.2, and if one gets a selling modifier that is greater than 0.8, the game will use 0.8.
This means the minimum purchase price will always be 120% of an item's real value and the maximum selling price will always be 80% of an item's base value.
I suspect these limits were added so that you would always get less for selling an item to a vendor than you would get from buying that same item from them, to prevent a situation in which those modifiers (if left uncapped) could allow you to buy an item from a vendor and then immediately sell it back to them for profit, which would make the whole trading system in the game pointless.
Do note that these limits will only ever apply when you get to 16+ CHARISMA (check the table).
Conclusion and mod modules:
Now have a better understanding of:
- Where the hell that Fallout 4 wiki formula came from.
- How fBarterMax and fBarterMin indirectly affect final prices calculations.
- How fBarterBuyMax and fBarterSellMax directly limit final prices to prevent the trading system in the game become pointless.
- How CHARISMA and different perks, items, buffs (and debuffs for that matter) can modify final prices.
With that in mind, I created two modules to affect barter price ranges, and barter limits:
- Expensive Barter Prices module changes fBarterMax and fBarterMin settings to be 25%, 50%, 75% or even 100% higher than their vanilla values, which in turn increase the BUYING PRICE MODIFIER and SELLING PRICE MODIFIER inital calculations, which then impact on the FINAL BUY PRICE and FINAL SELL PRICE formulas, thus changing their final prices while still letting your CHARISMA, perks, items and buffs affect those final prices normally.
- Rebalanced Barter Limits module changes fBarterBuyMax and fBarterSellMax settings to be 5%, 10%, 15% or 20% closer to each other to make the FINAL BUY PRICE and FINAL SELL PRICE closer to buying and selling at an item's base value (or 'real' value if you prefer).
(click the Vault-Tec logo to go back to the mod page)
2 comments
BASE PRICE FACTOR = 3.5 - (CHARISMA * 1.5) / 100
BASE PRICE FACTOR = 3.5 - CHARISMA * 0.15
Should that not be 3.5 - CHARISMA * 0.015? It looks like we divided by 10 instead of 100.
If true, then charisma would have only a tiny effect on buy and sell prices though.
The old Skyrim UESP wiki used the expression:
for the part of that ecuation that accounts for the skill level (Speech in the case of Skyrim), according to the wiki:
Since the Speech skill in Skyrim goes from 0 to 100 it makes sense for the ecuation to divide by 100 to allow for the possibility that if you have maxed Speech skill to 100 the end result would be 100/100 = 1, meaning it would have maximum effect on prices (as it should).
Applying the same logic, I can only assume the correct expression has to be to divide by 10 in the case of Fallout 4, since CHARISMA goes from 0 to 10, which would explain why the Fallout 4 wiki uses the formula with 0.15 instead of 0.015 as you are right, if that was the case it would indeed make CHA have far less impact on buy/sell prices and that doesn't seem to be the case in game.
I've edited the article, thanks for pointing it out.