Seems just in the past few years game costs have skyrocketed. 2010 and earlier it looks like $15M would get you a great AAA title with good marketing and everything (Gears of Wars, Left 4 Deads.) I'm guessing massive media blitz for modern games are really chewing up the budgets. Considering the companies own the IP most of the time, and seem to only be making sequals, so much of the materials (textures, engine, 3D models, animations,) already exist, just need to be refined/updated, I don't see why a 4x increase in costs is necessary. It also seems like Developers are shipping games before they're complete (I.e. releases feel like Betas,) now that they can patch their games via online updates, so quality control expenses should be lower than before when a game had to launch perfect because it couldn't be fixed. Also with many people giving free support by playing Betas and giving free feedback that area should decrease drastically cost wise.
That's why I feel the COD "insert name" being plastered on everything from my Tacos at Taco Bell, every other TV commercial, and even on kid's lunchboxes is really why the prices are screaming higher and higher.