It's no so much the visual damage as the actual damage.

My mom's C230 was backed into, looked FUCKED up, but only only about $3,600 worth of damage. BUT, her C220 looked untouched after being rear-ended... had about $3k worth of damages.

If it was rear-ended and messed with the gap between the door and quarter panel, I'd say it's probably got some frame damage as well as needing a new 1/4 panel, trunk, trunk floor, rear suspension/subframe...

I could definitely be DEAD wrong. I've never worked in a body shop or with insurance. This is purely off experience with wrecks