Well,
I just spent the last week, in Cowan Creek, on my late 80,s Cavalier 37 "liability". Great week, beautiful spot, lots of relaxation.
If the values in the original post are now typical she is worth around a third of what I paid in initial cost and upgrades.
I must admit this was not expected when I bought the boat, I bought a somewhat neglected boat at a around half the then market price and spent the difference on upgrades. That was 6 years ago. Prices have plummeted since then but we plan keeping the boat for many more years so the loss will not be realised until we sell.
I would gladly do the same again, the enjoyment gained makes the expense worthwhile. I would however always remember that boats are about enjoyment, definatley not investment!