This site makes for interesting reading. I've haven't bid on anything yet but the bids for just about everything from actual full-scale tank tracks to jet engines to dissassembled aircraft to pallets filled with electrical motors, wheels, and switches all generally start at $50. A dissassembled F-16 just sold for $2800. (http://cgi.govliquidation.com/auction/view?id=905733) They
even have a ca. 1960 US Navy blimp gondola up for auction right now - $50 starting bid!
As long as you don't mind buying by the pallet-load (or truck load) this might be a good place to get various electrical components, wheels, sheet metal, hardware, and etc. Maybe this would interest some of those thinking about producing a number of tank kits?
Anyway, I just thought I'd toss this up and see if anyone here ever purchased anything through this site? It looks a bit intimidating to me.