In 2010, the New York City-based restaurant Serendipity 3 revealed its $69 hot dog, winning the Guinness World Record for the world's most expensive hot dog. Served on a toasted pretzel roll with truffle butter and covered in foie gras, the award-winning hot dog made the restaurant's $18 cheeseburger seem like a steal. That's the point, says Professor Damon Centola of the Annenberg School for Communication at the University of Pennsylvania.