I can think of a good UK example. The Mini. Ten years ago I used to see them in the paper for £100, now, you couldn't get a body shell for under £600 with a standard example now worth well over £3,000! But that's a Mini. A Mini, a Beetle and a 500 have two things in common, they're practical and they're cult items. The C5 has something completely different, which is novelty value.
Why do you own a C5? For the commute? For the pleasure of riding it? Or because they're unusual, rare, and because you love the looks from people when you take it for a spin? The C5 is something Joe Public remember as a joke... and I say that as a devoted owner. People remember it, not for it's innovation or style, but because it was a total commercial and resulted in one of biggest financial disasters of any inventor.
So, sure, you take your Vincent, Beetle and 500 and keep on about how they suddenly became worth a fortune, and now let me give you some other examples.
Betamax. Need I say more? Total disaster. If you had a Betamax recorder in your loft, mint in box, unopened, do you think it would ever be worth the initial investment it cost to put it there? It was a disaster, people will smile fondly when you say that you have a mint condition Betamax recorder, but that's where the fun will end, because outside of a museum it will never be worth a penny more than it is now. Novelty value.
Sony Minidisc Player Designed to rival the CD. Mint boxed MiniDisc player now? If ANYONE remembers them, which itself would be a miracle, it's something that nobody would actually want. Novelty value.
Laserdisc A rival to VHS that predates the DVD... never caught on. HUGELY expensive new. Value now? Next to nothing. Ever likely to be?
Apple Newton Predecessor to the PDA. One of Apple's first products. Clever, intuitive idea that never caught on and cost the company a lot of money. In theory if you had one you COULD use it now, but it's unlikely. Mint boxed one? If you'd have bought one new it would have cost a LOT of money. Now, next to nothing.
The C5's fun to own, and it's fun to see the looks on peoples faces when they see one, but as an investment? You'd be better putting the money in the bank and leaving it alone. My C5 I'm very proud of. I use it, I take it out on runs etc, and I don't expect to ever lose money on it, but a mint boxed one, while probably steadily increasing at the rate of inflation year on year will never be worth megabucks. Why? It's a novelty that you can't see because it's still stuck in a box.