(I still like the idea of bartering.)
How about these ideas for bartering:
Idea A: Each item in your inventory has a value number. When you go to purchase something or make a deal or make any payment, the person you are paying lays down the price in value points. There would be a window that would pop up for you to place items from you inventory into until the value points meet (and maybe go over--but never under) your quota.
Idea B: Same as above, but once you reach your quota and submit it, the barterer then chooses a few items from the bunch (computer picks by random)
These methods would be used to purchase anything. Kinda like trading.
