more than 50 large collaborative works between 1984 and 1985. Despite criticism when these were first shown, Warhol called some of them "masterpieces," and they were influential for his later work. In 1984, Warhol was commissioned by collector and gallerist Alexander Iolas to produce work based on Leonardo da Vinci's The Last Supper for an exhibition at the old refectory of the Palazzo delle Stelline in Milan, opposite from the Santa Maria delle Grazie where Leonardo da Vinci's mural can be seen. Warhol exceeded the demands of the commission and produced nearly 100 variations on the theme, mostly silkscreens and paintings, and among them a collaborative sculpture with Basquiat, the Ten Punching Bags (Last Supper). The Milan exhibition that opened in January 1987 with a set of 22 silk-screens, was the last exhibition for both the artist and the gallerist. The series of The Last Supper was seen by some as "arguably his greatest," but by others as "wishy-washy, religiose" and "spiritless". It is the largest series of religious-themed works by any U.S. artist. Artist Maurizio Cattelan describes that it is difficult to separate daily encounters from the art of Andy Warhol: "That's probably the greatest thing about Warhol: the way he penetrated and summarized our world, to the point that distinguishing between him and our everyday life is basically impossible, and in any case useless." Warhol was an inspiration towards Cattelan's magazine and photography compilations, such as Permanent Food, Charley, and Toilet Paper. In the period just before his death, Warhol was working on Cars, a series of paintings for Mercedes-Benz. Art market The value of Andy Warhol's work has been on an endless upward trajectory since his death in 1987. In 2014, his works accumulated $569 million at auction, which accounted for more than a sixth of the global art market. However, there have been some dips. According to art dealer Dominique Lévy, "The Warhol trade moves something like a seesaw being pulled uphill: it rises and falls, but each new high and low is above the last one." She attributes this to the consistent influx of new collectors intrigued by Warhol. "At different moments, you've had different groups of collectors entering the Warhol market, and that resulted in peaks in demand, then satisfaction and a slow down," before the process repeats another demographic or the next generation. In 1998, Orange Marilyn (1964), a depiction of Marilyn Monroe,