Here's an interesting stat for you: almost as many people around the world play World of Warcraft as bought the Xbox 360 in the first year of its life. Or indeed just about any other console in the first year of its life. And they all pay a subscription fee. Putting it another way, there are more people playing WoW than the entire population of Greater London. Or, if you want it in cold, hard cash, conservative estimates peg the income from WoW subscriptions at about 100 million dollars per month.
No, honest, there's a review in there as well, read it here.
http://www.eurogamer.net/article.php?article_id=72120