World of Warcraft (WoW) has helped ATVI maintain its stock price, with this one single game providing roughly 30% of the revenue for the entire company via its expansion packs and monthly payments. Subscription revenue alone totaled $1.2 billion both in 2008 and 2009, and an additional $1.36 billion in 2010. Corresponding costs (the overhead cost of maintaining WoW’s virtual world) totaled a mere $404 million in the first two years mentioned, and $241 million in 2010. This means that WoW subscriptions have generated gross margins over 80% consistently. Since WoW has very high operating leverage any decline in revenue will have dramatic effects on the bottom line.
Forbes takes a detailed look into underlying finances of ActivisionBlizzard, and Vivendi's on-going efforts to sell its stake in the company. Diablo3 cash-shop revenues are not mentioned, but this would explain Blizzard's desperation to diversify from WoW subscription revenues.