Galves guide indicates the deduction for major collision damage (> $2,500). Granted that's sub-wholesale but it's some proof from an authoritative source. Many of the free appraisal sites do as well. You should not be asked to provide a release just by virtue of having them pay for the collision repair so worse case you can always threaten or even bring a small claims case for the diminution once the car is fixed. It's a pain bringing it, as you'll need an "expert" to testify as to the diminution, but it's cheap to file and that can often get them to cough up a few bucks. Many folks also find that when they mention their prior but fading hesitancy to bring a personal injury claim for the back pain they've experienced since the accident, the carrier gets more reasonable. I'm not suggesting you make anything up but if you did sustain some injury it doesn't hurt to make that known. It may bring a higher level claim handler into the mix.