I got one that was in admittedly terrible shape for a couple of bucks, but it cost like $15 or something to ship it the slowest way possible. That's okay, I cleaned up the mainboard and put it in my "new" SFC system that had issues and made one bitchin' system.
My "new" system cost like $60 shipped from Japan. I got assraped on that one, but it did come with new controllers and I was able to fix up the system, so I've got a boxed flawless SFC now.