Hey there gamer. Have a suggestion to make.
I think that there should be some kind of GUI to lookup specific items, and see if a market has it in stock and for what price, kind of like going to a retailers website to see if they have 44"" Flat Screen TV's in stock. This could be accessed by using the command /shop, as /shop is the same as /market.
This could be a simple GUI where you could just see which markets have what in stock, and maybe lookup specific items. You would still need to go to that specific market, and wouldn't break the whole Player Based Economy idea.
Let me know what you think!