$10(eBay) and up.
You could probably find some decent U160 controller for $50 or thereabouts, just make sure what interface you have on your drive before you buy the controller.
If you have some old server disk for example, chances are it'll be SCA(a rather wide connector sitting right in the middle of the drive, 80 pins, includes power and all), in which case you'll need a converter as well.