Of course some players like being able to get rich so this should be optional. With that said..
The real issue is that NPCs do not really have any needs. They don't buy anything from each other, they don't really use up food, they don't really use up supplies, they don't make any purchases, etc. Since there is no action on the market except what the player brings there is no responsiveness in the economy.
Most games (that are not turn based simulations) have this problem.
What might be possible is to have a running simulation in the background that updates once a game day or so. When you talk to a merchant a check is made to alter prices and stock based on that simulation. NPCs would never go anywhere in-game and they still would not really have needs, but within the simulation their stock/prices could be adjusted according to what is going on.
Adjustments could be tied into the game world based on quests completed, ongoing conflicts, perks, or factions pleased/hated. Merchants would need to say things like "Slow Town keeps getting hit by raiders. They bought up all the 9mm ammo." so the player could have some idea of how they could affect the supply of that ammo (go to Slow Town and wipe the raiders).
That would bring a little more responsiveness and interest to the economy without having to give individual NPCs a "need".
A player could still get pretty wealthy off this system though. In Fallout it is trivial to travel from one place to another - you effectively teleport there for free. It would be easy to find out some area needed 9mm ammo, get a bunch of it from elsewhere, and then sell it for 4x normal price.
To resolve this fast travel would have to have some cost associated with it.
The thing about all of this is that I'm not sure if it's "fun". It seems like it might be though. It definitely seems like a meta-game that could be implemented more or less within a mod if they didn't do something inside the game by default already.
Since you can build a "town" in Fallout 4 and your town has trading lines I am hoping they also implemented some kind of basic economy setup. Probably not anything quite as complex as I described, but...
Like you said, Vault Boy dreams.