The energy and atmosphere at an automobile auction is unlike anything else. It's a room packed with the world's rarest and most desirable automobiles in existence, bustling with the world's wealthiest people as they engage in heated bidding wars, throwing theirs hands up in agreement to millions of dollars with their eyes on these prized collectibles. Not only are the prices outrageous, but the actual stories behind these one-of-a-kind machines are just as impressive. With the end of a summer that saw the two most expensive vehicles ever auctioned in the world, it's time for a recap. Watch the numbers climb with this list of the 15 Most Expensive Cars Ever Sold at Auctions.