2013's second-costliest auction car: 1967 Ferrari 275 GTB/4*S N.A.R.T. Spider
$27.5 million

This Ferrari sold for what's believed to be the highest auction price ever for a "road-going" (non-racetrack) car, as well as the second-highest amount in history for any auto regardless of type.

Outfitted with a beefy 300-horsepower V-12 engine, the cabriolet is one of just 10 N.A.R.T. Spiders ever built ("N.A.R.T." stands for "North American Racing Team").

Road & Track put a N.A.R.T. Spider on the magazine's cover when the vehicle first came out, while late actor and car enthusiast Steve McQueen used one in the 1968 film The Thomas Crown Affair. McQueen even bought a N.A.R.T. Spider for himself and tried to buy this model after an accident damaged his.

A wealthy North Carolina businessman picked up the car directly from Ferrari in 1968 and kept it until his 2007 death, and his family had RM sell the vehicle at a California charity auction last summer.

2013's costliest auction car: 1954 F1 Mercedes-Benz W196 Grand Prix
$29.7 million

This super-rare racer garnered what's believed to be the highest auto-auction price not just of 2013, but of all time.

Knight, the Bonhams expert, says the W196 offered well-heeled auto enthusiasts a chance to buy "the talisman of any collection."

"No matter how good the cake is, you want the icing on the cake -- and no matter how good the icing is, you want the cherry on top," he says. "This car offered any collector the chance to buy that cherry on top."

Top race-car driver Juan Manuel Fangio drove the W196 to victories in the 1954 German and Swiss Grand Prix contests. Experts believe the model represented the first Formula 1 usage of such then-radical technologies as fuel injection and a "straight-8" engine (an engine with eight cylinders in a straight line rather than a "V" configuration).

Knight, whose firm auctioned the car off in England in July, says the model attracted big bucks because of its racing pedigree and uniqueness.

It's one of just four such vehicles owned by private parties rather than Mercedes-Benz, and the other three belong to museums or other institutions that seem unlikely to ever sell.

"If you wanted an F1, this was the only one available," Knight says.

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