First let me say I am new to the tandem thing, we (wife and I) just built up our first. I looked everywhere for 3 months trying to find a good deal on a late model unit: we are both mtn bikers riding hard tail 29ers. So I wanted flat bars and 700c wheels with tires as wide as would fit. Armed with a desire to try a tandem and our Mtn biking experience we decided to buy a new Frame Set from Cannondale and build up or bike to our taste.
So 2 wks ago I had my local cannondale dealer order me a new 2010 unit... medium blue is size large / small.
FSA cranks, disk brakes, DT swiss 40 hole hubs, X9 9 speed shifters, BB7 disc with 203 rotors, flat bars, etc... some used parts I had others found on sale here and there. Total build was a little over $2,000 and weight is 41 lb 11 oz on my scale. Thing is the bike fits us and our riding style...
Maybe you could build your bike... starting with a frame set... for less than retail of a complete bike...
I paid $1400 for the frame-set, it came with fatty fork, seat post clamps, headset, and with eccentric BB....