The TechZone talks about the business of selling virtual online game
treasures for real cash.

In 2002, Mr Castronova famously calculated the GNP per capita of the fictional game-world of "EverQuest" as $2,000, comparable to that of Bulgaria, and far higher than that of India or China. Furthermore, by "working" in the game to generate virtual wealth and then selling the results for real money, it is possible to generate about $3.50 per hour. Companies in China pay thousands of people, known as "farmers", to play MMORPGs all day, and then profit from selling the in-game goods they generate to other players for real money.

Trading Virtual Gold For Real Cash