In case you had not heard, World of Warcraft has 6.6 million subscribers. That works out to about $99,000,000/month in revenue. Here is a picture of how that makes other, hugely successful games look like a bunch of chumps.
Think about that for a moment. 0.1% of the planet plays World of Warcraft. The entire population of the planet Earth, including Tibetan monks, tribesmen on the plains, researchers in Antarctica, and the Amish: 1 in 1000 people plays World of Warcraft.