Benefits (health insurance, etc) often cost an additional 50% of a person's salary, so a rough estimate of total employee cost is $150k per employee who is getting $100k of that via a check, and the other $50k via other benefits.
Overhead (office, utilities, administrative support, computer equipment, training, etc) can cost another 20-50% above the salary per employee as well. For instance HR, accounting, executives, advertising, sales, support, etc do not contribute much to the game development directly, but they support the game in ways other than development.
The typical game development process is, I suspect, a lot more complicated than many people assume, and it takes 2-5 years to develop an a-list game starting from concept until release:
Begin with an idea or concept - some defining aspect of the intended game
Convince the developer (say, EA) to pursue it
Developer gets producers
Developer and producers get investors (the developer may be an investor, and may be the only investor)
Development is started
- Storyboard
- Project estimation
- Decide on game engine
- Start creating digital assets (often outsourced to smaller firms)
- Create character models
- Create object models
- Start creating maps
- Textures
- Rigging (putting "bones" in models)
- Animation
- Lighting
- Physics
- Technical elements (new features, such as waves in water, wet hair, vehicle physics, etc)
- much much more
Then you start on advertising, production, sales, support, etc
Each of the above takes a team of several people months to perform the task, then for several months after that they are tweaking things. There is a huge effort involved in integrating everything so it all looks good together and works well. While it would be nice if they could use the same rigging, animation, and character models they already have from previous games, they often do not because players can tell that this main character moves differently than that one guy in the other video game. Further, time is limited. If they start with one game engine, they have to release within 18 months or so before they are eclipsed by other games with a tighter development cycle. This forces them to spend more in order to get the work done faster, again, often by sending out some of the work to smaller firms.
In other words, producing a video game with even only 2 hours of gameplay is not much different in terms of time and effort as it takes to produce a movie, or even a new drug (drug companies are often lambasted for the cost of a tiny pill, but many people don't realize how much it cost to get them there).
Then you have to go back and remember that the investors at the top of the list want more money back than they put in originally. So even if the game only cost 12 million to develop, the game company needs to make 24 million just to break even because they have to pay back the investors. It's more complicated than that, as the investors do assume some of the risk, but the concept is generally that "development costs" are not a fixed figure.