They're also selling well because they're dirt cheap atm, if the prices go back up then no-one will want them again.
The price of the 350Z isn't ever going to rise back up, simply because it's a mass production car only just out of production. You could minimise loss by never driving it (I mean ever, on a brand-new one) and storing it in a barn for the next 40 years, then it may be worth about the same when it comes out if the Zed is even considered a classic by then. Failing that, drive it, enjoy it, and who the hell cares how much it's worth