Best way to put the gold sellers out of business is by making it a feature of your game.
I am very angry with Blizzard about this. They pretty much lead the charge against in-game items for real money, even going so far as to get Ebay to ban all "intellectual property" sales, even for games that didn't mind *Asheron's Call", or even supported it *Ultima Online*. Then several years later they change their minds and implement it into their games. Just a bunch of hypocrites.