The game is not extremely expensive, however, 1. it is for some regions of the world and 2. it might be when one thinks of it for the budget of a kid that a parent may have allocated. Several people trim their budget lately anyway and WoW can contribute in raising savings. This trend may continue or increase due to Peak Oil, but let's not go into reasons of the global crisis right now, it's off topic.
However, I also suspect the competition has started taking hints of wow's success and it may have started copying it well or improving it in other areas.
(Concerning the top news on the front page)