"The basketballs deteriorate" [LINK]
From an ARTnews article detailing the career of Jeff Koons:
“Equilibrium,” his groundbreaking 1985 show at International with Monument, included basketballs floating in aquariums, lifesaving devices cast in bronze, and reproductions of Nike advertisements featuring black basketball stars. The basketball tanks, in editions of two, originally sold for $3,000, and the lifeboats, in an edition of three plus one artist’s proof, sold for $8,000, but those prices doubled within a matter of months. In recent years a lifeboat and an aqualung have sold for about $2 million each at auction. Less in demand are the basketball tanks, whose top price at auction is $244,500, because, sources say, they are difficult to maintain and the balls deteriorate.