Was searching Corvettes for a club member for an autocross car and I noticed that the '08 and '09 Z06's in my mileage range (36k) are overwhelmingly in the 40k range. I found at least 30-40 cars in that price range on Autotrader.com. I paid $40k for my '09 3LZ 5 years ago.
With the new mid-engine and no more manual transmissions, my guess is it only goes up from here.
Just like the late 60's and early 70's, the big displacement engines are valuable. Mine's the last of the NA Z06 (That 7.0 liter is going to be coveted), which is hugely desirable for a track car. This forced induction crap has neutered Corvette. Find a C7Z that can complete a full 10/10ths track session without going into limp mode due to heat soak.
I guess the value is irrelevant at the moment, as I'll never sell it, and GWiz will inherit it, but it could be an extremely valuable asset for her in 30-40 years. Hell, both will. The race car only has 17k miles. It's just about to be on its 3rd engine.
