Action Comics #1 just broke the record of most expensive comic book to sell at auction. It was auctioned of by comicconnect.com, with the final bid of $2.16 million. The issue garnered such a price because it was professionally grade as one of the most pristine copies of this title.
http://movies.yahoo.com/news/action-comics-1-sells-2-16-million-auction-010326975.html