New York: A rare copy of Action Comics #1 that introduced Earth to Superman has become the world's most expensive comic book, selling for a whopping USD 3.2 million. The 1938 book in which the superhero first appeared initially cost 10 cents. When Darren Adams decided to put his incredibly rare, nearly pristine copy of the debut issue of the Man of Steel up for auction on eBay, he generously started the bid at 99 cents.