With me, it depends on how much time I'm likely to spend on a game.
The only games I tend to buy full price are JRPGs, as I know they'll most likely give me at LEAST an hour for every dollar spent. Then there are online games like Call of Duty which I can basically play for a year if not more. Games that you know will be worth the investment in time is what I tend to pay full price on.
For everything else, there's rentals, used game sales, or since I have a PC, Steam/Dealzon savings. I basically buy my PC games when they reach under $10, which happens the vast majority of the time, within half a year of release.
Exactly. For me its about how many hours I will be entertained. When you compare gaming to any other activity you can do outside the home, gaming is a pretty good value.