There is no real economy in Fallout 4. In vanilla you will end up with a ton of caps and nothing to spend it on, unless you're solidly into settlement building and spending caps on shipments, and even then the vendors can't buy most of your useless-but-good stuff because they don't have the caps.

Desert Empire Company Goods, like its originator, Whiskey Smoke, make you the economy. DEC adds later game mechanics to offload those caps in a lore friendly way. If you set up your settlements right they will be producing magnificent amounts of crop ingredients, and you just need to craft the items. Same problem early on, of course, being that vendors don't have the best cap store, so I suggest Vendor Caps listed as optional in the required mods (or something similar, obviously).

So, later game once you have Caps Collector and the trade caravan post, etc, you can build a Quartermaster box to help you "sell" wholesale right there in the settlements. Depending on your choices interacting with the box, the caravans will take a tiny cut or a big cut right there through that Quartermaster box. However, that just means more caps right? Caps you can't spend your money on? Wrong!

Additional buildable signs (you NEED all three in any settlement, found in the Whiskey Smoke workshop menu far left) offer a way to offload those caps for happiness benefits. Interact with those signs to 'pay' for maintenance of your settlements. These maintenance items are just a way to offload the caps, but in a lore friendly and interesting way.

In addition to that, adding those signs shows your settlers you are a businessperson of some note. IF they notice you're hoarding caps, happiness might take a hit. IF they notice you don't have many caps at all, happiness might take a hit. It's a balancing act, and this happens by way of my mod. 

How I Solve Economy

I want you to have fun spending caps. I want you to have fun earning caps too, but also keep a tight fist on your caps so you maintain 4k to 6,000 caps in your pocket. Inside that envelope the game will provide the best benefits to your settlement in which you have those three signs. Each settlement MUST have all three signs if you want that settlement to benefit. They are a way to tell settlers the success of the settlement and the revivification of the Desert Empire Company, and to “post” that they need maintenance funds (RP-speaking, but in game they’re just signs with underlying code; interact with the signs to makes choices, caps get spent, Bob's your uncle).

IF you are slightly outside that 4k to 6k amount of caps in your pocket, the benefits will be less, a meager reward as Danse might put it. However, if you have less than 1k caps or more than 10k caps, the benefit will be negated and settlement consequences will be strong. Who wants a boss who rolls up in a Rolls Royce when they’re sitting in a wobbly chair they had to wrap in duct tape to keep from falling apart? Or worse, you clearly can’t keep a handle on your caps, you’re a poor slob, and maybe they won’t be as happy working at a settlement that has that kind of haphazard boss.

These optional items are available in the workshop menu when you accomplish the quest for Kessler (RP, and very immersive) and also Caps Collector 3 in some cases. By that time you will have settlement surpluses to sell off en masse and probably way too many caps anyway as even the most brutal survival mod rarely solves that vanilla problem in later levels.

If you use a mod like Uncapped Settlement Surplus, the vanilla system of preventing the workshop from filling with many food, drink and caps/day is removed. Settlement attacks happen more frequently when you have a lot of stuff stored if you turn off the option in that mod, so use the Quartermaster station to good effect!

Welcome to the You Economy(R).