There's cosplay, where kids coble together their own outfits using stitches, fabric and rubber, and then there's cosplay, where an official costume from a game is made commercially available. Like this one, for American McGee's Alice!
Available from Party City, it'll cost you (or that special, role-playing someone in your life) $60. For that, you'll get the dress, a skull bow and necklace, with those strappy shoes sadly not included.
You'll also have to find your own mangy cat and set of giant knives.