Yep, it's not cheap. People need wages just like any other job. The last couple of Call of Duty games for example cost over $200 Million dollars to make and had over 1000 people working on it.
That's a lot of money for making a new cover, redesigning the menus, and hiring new voice actors, and making new commercials. I mean the rest is recycled from the previous game right?
But yeah, there's a lot of stuff the large "Triple A" companies need to consider and spend in.