"Supply and demand are still driving prices," he said. "You have more millionaires being created, and a small number of these top-quality cars. It's also generational. The people who made large wealth are at a point in their lives when they want to collect these cars."
He said unlike other bubble periods—like the early 1990s, which was fueled by Japanese buyers—this market is far more diversified and global.
Still, Hagerty said, this year was such a big year for cars that "I wouldn't be surprised" if prices cooled a little next year.
The big news in 2013 was the race between a 1967 Ferrari and a 1954 Mercedes-Benz W196R to become the most expensive car ever sold at auction. The Ferrari was expected to win the prize at an RM Auctions sale in Monterey, Calif., this summer. But just weeks before the sale, the Mercedes race car sold at a Bonhams auction for an unexpectedly high $29.7 million. The Ferrari ended up selling just short of that number, for $27.5 million.
While collectible car experts say there are plenty of cars that have sold in private, nonauction sales for more than $30 million, those sales are difficult to verify.
Car sale for $100 million?
Hagerty said there will likely be a sale of a car for $100 million or more in the next three to five years. While there are several cars currently for sale at $100 million or more, none have traded for that amount yet.
"In the next three to five years, we will see a $100 million car," Hagerty said. He added the $100 million sale would likely be a Ferrari GTO—"the holy grail of cars," since only 39 were built.
(Read more: Even Santa can't help now—LaFerrari is sold out)
Here are the top five most expensive cars sold in 2013, and the most expensive cars ever sold at auction.