Koons, more than any other artist, has embraced the new possibilities that open up when you can charge seven- or even eight-figure sums for a single piece: his art is like the new luxury apartment buildings going up in Manhattan, which only make financial sense once the residences inside can sell for more than $5,000 per square foot. Koons’s art might be empty; it might be banal. But Koons does something very interesting, which very few other artists do. He turns money into art, rather than just turning art into money.