Let's say that a game like Killzone 2 or FFXIII takes 3 years to develop with a full team. Let's say that the team is about 250 persons. You have 40 persons working on CGI, 40 programmers, 145 artists (3D models, textures, animation), about 10 management guys, 5 audio/sound effect composer and 10 QA leads. Now, let's say those people are paid about 55k per year (it isn't that much for a big studio). It costs then 41 250 000 for the production team.
Now, add testers (that aren't paid well but there are a lot of them), voice actors (if you take John DiMaggio like Gears of War, it's pricey), legal fees, marketing, etc. Then, I suppose you are closer to 70 M$.
There you have it. High budget games cost a lot because making beautiful 3D models is an extremely long process. I read somewhere that in GTA, each artist was making like 1 or 2 streets.
How many cups of darkness have I drank over the years? Even I don't know...
