The steel pad I purchased from amazon.com was roughly $200. If you want a top of the line arcade style pad, it will cost you about $300 but if you're serious about it I think it would be sooooooo worth it.
I'm so happy to hear all the responses from you all who love playing DDR for your exercise. To those of you who are playing the newer DDR games (extreme or supernova versions) and have playstation 2 online hooked up, I'd love to play against some of you online some time. Now THAT would be fun.
Anybody interested?