If it were to go any cheaper I'd say $5 at the least. If you have the time and are going to play it I think the $2.50 difference won't matter. The game gets repetitive after awhile but is still fun and will suck up a lot of your time. Kind of like that kingdoms of amalur. Definitely a satisfying game though.
Here's some tweaks I used when playing the game. http://forums.gearboxsoftware.com/showthread.php?t=79043
I tweaked the intro movies so I didn't have to watch them every time I started game and disabled the mouse smoothing.