Where you could sell and trade items.(selling for coins) there would have to be a top price that you could sell it at reasonable price, it would be based on how rare it was how much it they bought it for and other factors. It would be a good way for people to buy what they want, and people to sell what they don't want.(trading)One person ask the person if they want to trade for the item they are trading, then the other person puts up the item they will trade the other item.