This isn't about 10 other friends fraudulantly cashing in on 1 bought game. This is a trade, whether for cash or other suitable recompense is irrelevant. Nothing is being fraudulantly traded. Why would I be allowed to buy a second hand Diablo 2 for cash and yet not buy it for something else of equivelant value?
Fraud is illegal (and quite rightly so), trading is not illegal otherwise you would never be able to sell even your car. It matters not what you are trading/selling it for.