ANet could do what CCP does with ISK buyers in Eve online: Set the player’s wallet to a negative amount equal to what the player bought. Therefore the player has to work off their ill-gotten gold and they’ll think twice before buying it again. Honestly, buyers are part of the problem, Anet needs to make a statement that RMT is unacceptable. It promotes account theft and exploitation of the game. Monitor money amounts, if a player’s daily income goes beyond X standard deviations of what they normally make, flag the account and watch it.