I have followed the collector car market for several decades, some a little more intensely than others. Ferrari remain my absolute favorite as a brand, though I admit that the Mclaren F1 is still probably my single individual car favorite. I had a small brokerage company (SMS Specialty Motorsports) through one bubble period in 87-89, just when Japan lost it's footing.
Some of the prices achieved during this year's Scottsdale pilgrimage are at seriously dizzying heights. Anamera provides a valuable summary of some of these results HERE.
I recall that less than 10 yrs ago, a 250GT SWB broke $1MM and then $2MM > last night, one (of great provenance of course) broke $8MM. Staggering money. Another $8MM for a 250GT LWB Spyder. Sales at 2 auction houses cleared $50MM in one night (HERE and HERE). Though maybethis should not be a surprise in the land of ZIRP and CB's Instant Tellers and Printing Presses. Porsche RSK for $3MM. A One of One Plum Crazy Hemi Cuda Convertible sold for over $1MM. A '69 Mustang Resto-Mod sold for over $300k.
While there have been stories in the wake of some of these events that examine the creation of a new asset class, the collector car asset class. The added benefit is that some can be raced, or shown in the Concours, huge social and entertaining events. Don't necessarily get that from a share or ETF certificate unless you consider the annual general meeting such.
Rarity. Provenance. Ownership History. Patina. There are many factors that give the collector car its 'value'. I think though it is also well worth remembering that something is only of any particular value if someone will pay you that for it. So just as for gold, silver, and almost anything, the value is relative. It produces no income and appreciates on speculation. Someone buying it now has an expectation that it will appreciate. Markets generally have a tendency to correct, and timing is a very critical element in that process. For those that 'exercise' their mechanical thoroughbreds, they enjoy the journey. (Financial) Yield seekers might get disappointed.