Owner: Ekaterina Rybolovleva, daughter of billionaire Dmitry Rybolovlev
Purchase Price: $88 million in 2012
An LLC associated with the Russian heiress scooped up the Central Park-facing 6,744-square foot penthouse for the full asking price, less than six weeks after it came to market. At roughly $13,500 per square foot, it's the most expensive sale by square foot ever in the U.S.