They don't make new XBox controllers, so if you're lucky enough to find some left over (my local Sears still has some), they'll be full price. Go ahead and bite the bullet - they won't be getting cheaper.
Well they don't make them anymore, and every store replaced them with the S controller. I have one that is brand new, came with the system, but I use a Pelican Wireless controller. PM me if insterested.