Estimated Worth: $40 Million

One of the most influential British artists of the twentieth century and an important contributor to the Pop art movement in the 1960s, Hockney continues to push the limits of his art and their prices. In 2009, his Beverly Hills Housewife, a portrait of art patron Betty Freeman, featuring a William Turnbull statue, sold at Christie's for over $8 million. He debuted a show last month at the Royal Academy of Arts in London, and even painted some of it on an iPad. Let's see how well that goes over on the auction block.