@Sky
In Mount & Blade the shop owners and merchants have an indicator showing how much money they have to purchase things from the player. When the settlements change from rich, to poor, and visa versa the shop owners money changes with it. This is usually altered based upon how many caravans successfully trade with said village. So if a lot of the cravens to Ulman (the only city in my game) didn’t make it to there destination because of pesky bandit raiders, then that city would ultimately diminish in wealth, this could then be reflected in how much the shop keepers are willing (and able) to purchase from the player.
If OverHype decided to adopt an economy similar to Mount & Blade, a system that includes the shop owners wealth would really work.