I think the biggest hole in the "best bang for your buck" theory is a figure that can never be judged in dollar figures.
Entertainment.
Funk, Shamus, and many others have great fun playing WoW, and I can appreciate that. But they get something from it I've never been able to. They have fun. I tried WoW, and I never had all that much fun with it. Sure, maybe I could get 4 cents an hour from it, but if I'm not having fun, is it really money well spent? Sure, maybe when it works out I might only end up getting about $2.50 an hour from a game like inFamous, but if I'm having fun, it will always be money well spent in my eyes.
Sorry, I got a bit rambly. If my post isn't clear let me know and I can clean it up tomorrow, feeling a little dead tonight.