A seminal Warhol — one of the artist’s first silk-screen paintings — came on the block at Sotheby’s auction of contemporary art on Wednesday night. Bidding opened at $6 million for “200 One Dollar Bills,” which soared to $43.7 million (including fees). Also, the artist's 1962 sketch of a roll of cash topped expectations when Larry Gagosian, the Manhattan dealer, bought the work for $4.2 million. Laurence Graff, the London jeweler, paid $6.1 million with commission for a 1965 Warhol self-portrait...