When I was looking for a boat, I plotted the prices of all the boats I could find in the 35 to 40ft range. It was noticeable that depreciation worked quite well up to twenty years old. Prices stabilised around twenty to thirty years old and then went wild older than 40 years.
I think this means that boats built pre-1960 need a lot of love to keep them on the market, or even afloat. So there are some ancient beauties that are commanding high prices, but there is also a lot of scrap out there pleading for rescue.
Steel and Ali hulls have a scrap value.
Ferro concrete and GRP - how do you dispose of them?