Lots of people say things like 'RARE legendary' in eBay auctions for DX7s and Casio VL-Tones, but eBay item #300001522431 doesn't go for hype, just saying "prototype VOCODER of german 70´s Electronic Pioneers". What's on offer is Ralf & Florian's vocoder, built to order by a local electronics company, and later used on the intro to 'Autobahn'. No bids so far at $3,800, with ten days to go. (Thanks, Kaden)
UPDATE: It went for $12,500!