I was talking to a body shop about unibody construction in the context of some rust repair several years ago. Basically, for a lot of cars, if it isn't a bolt o

I was talking to a body shop about unibody construction in the context of some rust repair several years ago. Basically, for a lot of cars, if it isn't a bolt on part, it's already supplied as one big piece from the manufacturer. Like, the whole side of the car sized piece. Whether that's one stamping or several welded together (or bonded), it's a cut and weld job for a collision repair. A small enough rust repair can be made up from sheet metal, but not a serious collision. Also: paint. It's never one panel. They usually have to feather in the color on the adjacent panels because getting a perfect match is tough despite computers, etc. You need one panel painted, and you're pretty quickly looking at getting 3 or 4 painted (or at least attended to). Even discounting airbags, it doesn't take much to total out even a five to seven year old car these days.