a AAA game it may be $10 or $15M. That only covers development cost.
No chance, not even close - a studio with 150 people, an average salary of $80k, and a 24 month development turnaround costs $24 million in salaries alone. A studio like 343 had around 350 developers at peak on their payroll during the development of Halo 4 and a development time of three years. With the studio based in Seattle and hiring top-tier staff, the average salary probably met $120k - salaries in that peak period would have cost a cool $3.5 million for just one month. If you're averaging just half that number across the entire project, you've spent over $60 million in salaries alone.
This doesn't include the enormous cost of their outsourcing operations - Liquid Development, Digital Extremes, Certain Affinity were involved (multiplayer content?). Other listed outsourcers include Axis Animation, Cynergy, Digic, Giant Studios, Pearl Digital, Sequence Group and Technicolor Game-Sound. It doesn't include the cost of running the actual studio, their hardware, software licenses for 350 developers.
Then there's the marketing.
Do a little research and just think about what was involved, then crunch some numbers. It's pretty mind blowing. I'd say the real world development cost of a game like that could very easily be in the region of $300 million.