collision chaos

my roommate hit the back of my 2006 grand Cherokee the other day. he cracked the bumper in a few places and left some scuffs. I took it to the auto body for an estimate and it turned out to be around $800. They want to replace the entire bumper. are they ripping me off? there are 2 cracks one in the center which is about an inch long and the second is on the bottom lip of the bumper. is there anything inside the bumper that could be broken? or should i just get the cracks fixed?

If by 'cracks' you mean the bumper is completely broken through than yes it would be more cost effective to replace the bumper. They can be fixed, but after your labor costs you would more than likely be paying more than you would have if you just got a new one...