Pirates of the Caribbean: At World's End (2007)
Budget: $300 Million
Which movie's budget surprises you the most? Either that it actually cost that much, or that the studio would actually pay that much.
Some likely contenders like Avatar does not have a listed budget, but no matter how expensive, that wouldn't be all that surprising.
Discuss this poll here: http://www.imdb.com/board/bd0000088/thread/224769095