After Sonnabend’s death in October 2007 at the age of 92, the estate tax return pegged her total worth at $876 million, triggering a $471m tax bill. Her heirs subsequently sold a portion of her postwar-art collection for $600 million—reportedly the largest private sale in history. Although the family had been in talks with the auction houses, they chose to sell parts of the collection privately because of the uncertainties surrounding the financial markets during the 2008 crisis. Backed by members of the Al Thani family, the art-dealers collective GPS Partners purchased $400m of paintings and sculptures dating mainly from the 1960s on behalf of private clients. This first cache is said to have included Jeff Koons’s 1986 sculpture "Rabbit", which has been valued in excess of $80 million, as well as Roy Lichtenstein’s cartoon painting "Eddie Diptych" (1962), Cy Twombly’s abstract "Blue Room" (1957) and Andy Warhol’s "Silver Disaster" (1963), one of the artist’s paintings of an electric chair. The second transaction, a selection of paintings by Warhol, was sold to Gagosian Gallery for a reported $200m. Among the Warhols sold by the heirs are "Four Marilyns" (1962); two paintings of Elizabeth Taylor; and three small paintings from the artist’s “Death and Disaster” series.