Game testers : £10,000 - £15,000
Graduates : £17,000 - £20,000
Experienced Developers : £40,000 +
They could have use the Microsoft programing language XNA, but since it is a professional $60 game they probably used a better more expensive software, or started from scrach.
It can because once you die the atoms in your body will still be functioning. if those atoms mix with ununpentium it can reanimate corpses, but they will not be alive. this means they would be able to move, but not speak or attack people. anyway you would need an aw-full lot of the element and you would also need it to keep channeling through your body.
Treyarch has released a "mod tool" called "Radiant" that is compatible with Call of Duty: World at War, and possibly others in the series to design custom maps (currently for Zombies at the moment). Treyarch may or may not use this tool. They may have their own to create maps. The Call of Duty requires more than just map builders in 3D programs to create Call of Duty. Game engines that run the game and keep score of players and allow players to move around are needed too. It may require up to 20 different programs and tools to create just 1 game, not even just Call of Duty.
Treyarch and Infinity Ward are two separate companies. the Modern Warfare series is a storyline on its own, and the Black Ops Series is as well. As for the first CoDs, they are based on actual history.
The basic concept itself is far older than any game. No individual has claimed sole credit for the idea.