Sometimes these experiments work: it turns out you can charge people infinite amounts of money for them to buy random progression objects in "Flash" games (nobody actually uses Flash anymore, but you get the idea -- it's those little games).

Sometimes these experiments fail spectacularly, such as in the infamous Diablo III Real Money Auction House: it turns out that you cannot have dollars inside MMOs. You can have them outside the game, on eBay, but not in the game.