Just checked out eBay and all but one of the ones there have a double-the-real-value-buy-it-now-price (I think I'll submit that to the Oxford dictionary as a new word suggestion). The bidding starts at £0.99 on the other one, though I bet the seller has put a silly reserve price on it. The swindler!
Edit: I've just had a reply from the manufacturers. They tell me that the joystick will work with the Mac if you're running the Jaguar edition of OSX, or if not, providing you have USB Overdrive (or similar I'd imagine) installed - there mustn't be any Mac specific drivers available. Yipee!! It looks like I'll be getting one then.