You do know you can save $50 every time you buy 10 versus just 1 right? At CrustCrawler you can anyways. I don't see used ones going for less than $30 a pop. $600 is still quite a chunk of change. If it doesn't work for you, you might have to rethink your crawler project (which I am assuming it is).
Oh yeah, you might also want to post on Seattle RObotics. For buying or selling used things that are so specific you really have to go to the places where people that use them congregate. THis is a general electronics forum and not a terribly buying/selling one at that.
Hi thanks for that. I'll have a look at the seattle forum. I am off to the USA in October on holiday. I'll have a laptop with me and will be scanning ebay ;-)