Over the past two decades, a few American classic cars have sold for prices that left many gearheads' jaws on the floor. Vehicles that cost close to nothing in the 60s are now selling for seven figures – cars such as the rare 1967 Chevrolet Corvette L88 that sold at a 2014 Barrett-Jackson auction for $3.85 million, or the 1966 Shelby Cobra 427 "Super Snake" that sold for a whopping $5.5 million at the same auction in 2007.