What do you learn when you sell a painting?

That you didn't charge enough:

In 2008, the estate of a Canadian woman, Lorette Jolles Shefner, filed a lawsuit in U.S. district court in New York against Maurice Tuchman and Esti Dunow, two experts on the French painter Chaim Soutine, and the National Gallery of Art in Washington. The estate claimed the experts had misled Ms. Shefner into selling them a 1923 Soutine painting, titled "Piece of Beef," for $1 million in 2004, and then resold it to the museum a few months later for $2 million. As part of a settlement, the National Gallery sold the painting back to the now-deceased woman's estate, and the two experts paid the estate $210,000 without admitting wrongdoing.