Length of the game determines the price?

[SundownKid]

I would probably more than double the prices. 2 hours = $5-10, 5 hours = $10-15, 10 hours = $15-20, 15 hours = $20-25.

I wouldn't release one longer than 15 hours, IMO people aren't willing to pay more than that for your typical indie game. If you want to make one longer, consider splitting it into a sequel.

(Of course, this can be totally dependent on the type of content and quality. I am assuming a pro-level of quality for the game).