My personal bests on ebay:
Trek Y-Foil CF beam frame - new, never built: $600
Zipp 404 (2002 model) in tubular, with 4 used tires: $650
Cinelli RAM bars - slightly used, but not a scratch: $250
Nike Hautacam shoes, CF sole, new: $90
But that's with a lot of patience. I'm now looking for a TT frameset in 59-61cm. Patience...
I also dumped some slightly obsolete digital camera equipment last year at a handsome price, far more than I thought it was worth. I wanted a Cateye CDW300 wireless cadence computer. ebay prices were $110-120 plus various shipping charges, from an unknown seller. I bought it from cbike.com for $120 with a modest shipping charge.