Or the effort spent to resell is valued more than the resale value of the game (whether it is true or not) or it's because COD has a higher resale value.

Although I'd guess that people's gaming budget isn't as simple as X number of games @ $Y max each and so-called blockbuster titles could easily start charging more without losing too much of their fan bases.

They could go for a bigger % cut of gamers disposable income, the same way smartphones have done for the cellphone market.

Videogames are also somewhat addictive, so the supply curve might look more like tobacco or alcohol.

About DLC, those can't be resold, plus they're useless if you don't have the original game any more. So they are kind of a lock-in tool. Which is, by the way, why I abhor them.