How ahead of his time was the pop artist? A silkscreen of Marilyn Monroe made by Andy Warhol is expected to be auctioned in May 2022 for up to $200 million. Christie's, the auctioning house, declared it "one of the greatest paintings of all time". But here is the fascinating part: there are many others just like it, all made by Warhol as well. John Gapper examines the benefits of mechanical reproduction for artists, something that Warhol "grasped early on."