In the last game developer salary survey the average salary of an American game developer was over $75,000 per year; when you factor in all of the costs associated with employing a developer (benefits, office space, support staff, etc.) the cost per developer year is probably (far) more than $100,000. We know that games on the scale of Metal Gear Solid 4 have 100 to 200 person development teams and these projects can span 2 to 3 years.
When you combine these two statistics, the range you get is $20,000,000 to $60,000,000 (which is pretty much the range we have heard industry insiders and analysts claim). All games are not projects on this scale, for example a game like Guitar Hero 3 probably had a much smaller development team (guestimate 50 people) and a much shorter development cycle (guestimate 12 to 18 months).
Now, when you compare apples to apples between the PS2/Wii and the XBox 360/PS3 it has been claimed by several well respected developers that the development cost has increased by 3 to 4 times. This is (mainly) because of how much more expensive it is to create the artistic assets for a XBox 360/PS3 game, and how many more of these assets you need to create in order to have a convincing environment; those minor details in XBox 360/PS3 game, regardless of whether it is shiny-bumpy metal or that every desk in an office now has pens, were created by someone at a cost.
