How much would it roughly cost to get a dress like this made?

I've grown to like this dress http://images2.boxwish.com/profile_images/profile/4437/context_00003_harry_potter_and_the_goblet_of_fire.jpg what I'm wondering is how much it would roughly cost to have a dress like that made by a seamstress, considering that its made of chiffon and silk and looks like a hard dress to make.