This is something I learned from a friend who gear upped his 210 due to a mechanical failure. He got a good price and insured it for that amount.
You insure for 75k and have an incident. They find out what scrap value, and let's say that's 18-20k. They subtract that from the insured value. So once your damage comes close to 50k, they total you. Easy to total a vintage plane since prop and engine are so pricey. Add some sheet metal and labor, and you see where this goes.
I'm not an insurance expert, and I just heard this second hand, so take it with a grain of salt.