If you take the size of the development teams (coders, IT support, play testers, artists, sound teams, media teams, sales and public relations, team managers, and on and on and on) coupled with the average wages and benifits for people of their skill level, you have a heafty dollar value that needs to be recouped before a single dollar of profit is seen.
Sure, but all of those things are what the cost of the game is designed to pay for. At least, traditionally speaking. When you are adding a new revenue stream, you really should only be focused on the costs that are associated with developing and supporting that stream - the other costs were always there.
The ~15%(applied however many times on monies in and/or out) is what their research and statistical data tells them the market will bear to maximize a ROI in the shortest time possible coupled with box and digital sales of the game. This could go up over time and could go down depending on all the afore mentioned variables.
Again, probably true, but I'm not sure where you are going with that. As customers, are we supposed to be happy that Blizzard is attempting to maximize their ROI at our expense? If they decided they could increase their ROI even more if they charged people $15/mth like WoW, should we all just sit back and be happy about it, because, hey, Blizzard is maximizing their ROI?