Unfortunately, I think you are hosed. You probably would have had to have taken it to a couple places and got estimates before turning it in. Even then, there could be language in the contract to negate that helping you out. Also, looking at the pictures, I wouldn't have expected that high of a bill either.
Something to be aware of when renting for sure. I can't believe the insurance doesn't cover the top, front and bottom. Isn't that convenient when those are the areas most likely to get damaged in simple mistakes....
