As of May 22, 2012, there's a new restaurant behind the Guinness World Record for most expensive hamburger: Serendipity 3 (225 East 60th St.).
For the mix of Japanese Wagyu beef infused with 10-herb white truffle butter, seasoned with smoked Pacific sea salt, topped with cheddar cheese, black truffles and a fried quail egg; and served on a gold-dusted campagna roll spread with white truffle butter; and topped with blini, crème fraiche and Kaluga caviar, you must spend $295.
The restaurant needs 48-hour notice before preparing the monster. The burger arrives stabbed with a "solid gold 'Fleur de Lis' toothpick encrusted with diamonds."
[via Design Taxi]