I don't consider videogames so much a product and buying games to me is more like supporting what (and who) I like and want to see more of.
So for me it's in order of importance:
1. enjoyment
2. quality
3. the amount of work that must've gone into it
4. favor
5. length of the game minus padding
Example: even if I liked Minecraft, I would still consider it overpriced, even before millionaire Notch became a multi-billionaire. For a game like XCOM, I didn't hesitate to chip in and buy it full-priced. If I want to see more turn-based tactical combat, a game like that has to succeed in making the publisher happy and willing enough to fund a large team.
So for me it's in order of importance:
1. enjoyment
2. quality
3. the amount of work that must've gone into it
4. favor
5. length of the game minus padding
Example: even if I liked Minecraft, I would still consider it overpriced, even before millionaire Notch became a multi-billionaire. For a game like XCOM, I didn't hesitate to chip in and buy it full-priced. If I want to see more turn-based tactical combat, a game like that has to succeed in making the publisher happy and willing enough to fund a large team.