For you folks looking for used tandem, check out the spring '08 issue of Recumbent & Tandem Rider Magazine (rtrmag.com).
The classified section lists at least a dozen used 2-seaters (and one Triplet) for sale!
Varying in price from a collectible/rideable/restored Saxon @ $450 (or best offer) to several Treks, Co-Motions, a Bilenky Viewpoint (hard to come by used), Meridian, Vision and Bike E (recumbents), 'tana and C'dale with prices from $700 to $7500. Who says there are no used tandems on the market?!
Also good tandem article on a prototype daVinci Grand Junction.
Pedal on TWOgether!
Rudy and Kay/zonatandem