That's actually the Blizzard division's profit. So $550 million is what they make after all expenses, including R&D on the next game, payroll, servers, bandwidth, etc.

By the way, I'm not personally one of those people who complain about how much money they make compared to ingame service. They've made some poor decisions in terms of when to release stuff and what capabilities to give the GMs, but overall they're running an excellent service. At this point it's much better than any other MMO, by far. I just thought it was interesting to see the real numbers of how much they're raking in.