Sean Connery cost himself $US450 million when he turned down the chance to play Gandalf in the Lord of the Rings trilogy. The former James Bond actor was offered 15 per cent of the franchise's box office takings. Despite that, Connery turned down the role because of his concerns over the script and it eventually fell to the lesser known British actor Ian McKellen. The Rings trilogy went on to make $US2.9 billion in box office takings, with the first film alone raking in more than $1 billion. Had Connery accepted the Gandalf role, his 15 per cent of those takings would have been worth $US450 million. His last known net worth is $US300 million.

At the time, he accepted a part in the critically panned film The League of Extraordinary Gentlemen, which lost $US12 million at the box office. He has since retired from acting. Connery has never confirmed he turned down the Gandalf role, but has admitted he never understood the script, saying: "I read the book. I read the script. I saw the movie. I still don't understand it. Ian McKellen, I believe, is marvellous in it."

McKellen has reprised his role as Gandalf in The Hobbit trilogy, which has been just as successful at the box office, with the first two films earning $1 billion each. The third hobbit film, The Battle of Five Armies is set for release on 17 December 2014.

Other worst career decisions by actors:
Will Smith turned down the role of Neo in The Matrix.
Hugh Jackman reportedly refused the part of James Bond in a reboot of the franchise. It went to Daniel Craig, who is now the highest paid Bond in history.
Matt Damon and Jake Gyllenhaal were both reported to have turned down the lead role in James Cameron's Avatar. It went on to become the highest grossing movie of all time.
Mel Gibson turned down the part of Maximus in Gladiator. It netted Russell Crowe an Oscar for best actor.
Jack Nicholson turned down the iconic role of Michael Corleone in The Godfather, saying "At the time I believed Indians should play roles written for Indians and Italians should do the same."

Source: The Internet