I'd like to give some insight here to the high end trading because it is actually the complete opposite at the moment. Caps are not being accepted most of the time for the majority of the high end items now because they don't value caps at all. What a lot of people might not yet realize is there is actually a cap to how many caps you can hold, which is 25k. If you're lucky enough to find someone to sell you a two shot explosive shotgun for example for caps they would still only sell it for well above the limit, meaning you would have to have mules with caps who trade them to their mules. You can also only list an item in the in game trading for 5k max, which would be considered a lower-mid end legendary sale right now.

This also creates a trust based trading system either way where it is easy to get scammed. A middle man is almost required to be safe and either way the trade is still very tedious.

The people earning these caps at such a high rate aren't using vendors typically and it isn't a problem noticed by casual players yet. It will be eventually though as they catch up by vendoring items only to one day be surprised by the game telling them they can't earn anymore caps.