WoW is not utopian capitalism, there is a government (developer) who sets rules, names prices, and protects lesser characters to maximize the enjoyment all people get out of the game. Also, not everyone is a capitalism starts out on an even playing field, people with wealthy parents have a distinct advantage over people with poor parents. If anything, WoW is socialist in that it makes everyone equal and gives them equal opportunity (and this is strictly enforced by the developer who doesnt allow players to buy items and gold with real money).
Games with 'socialism' are games where everyone is equal all the time. Most multiplayer games (FPS, RTS) are like this. In fact people complain if a game is not equal because someone is hacking or someone else has different weapons (BF2 comes to mind when they let people who bought the expansion pack were able to use the new weapons when playing people who just had the vanilla game).
