It is understandable that The Girl With The Dragon Tattoo did not get the commercial success that all its fans felt it deserved, what with its lengthy running time and hard R-rating, but MGM was originally hoping for much better than the loss they have ended up with (it should be worth noting that The Girl With The Dragon Tattoo took in $231 million worldwide, but the film still ended up below MGM's expectations, and have made the studio lose a certain amount of money).
The reduced budget will of course affect the sequels The Girl Who Played With Fire and The Girl Who Kicked The Hornet's Nest, but what's interesting is David Fincher's position within the context of the sequels. It has been postulated that simply hiring David Fincher has cost MGM $5 million, but Fincher can't be simply removed from the project as he holds an option for the first sequel (said to be Fincher's favorite story in the trilogy).