Well, I've seen 42" Sampo plasma units go for as low as $3500 on Ebay and Ubid. Though still able to do HDTV, they're of lower resolution than the current standard. You wouldn't know the resolution is less until you compare to the nicer sets.
On the other hand, $3500 would get me a chip and GHL header with muffler, or a slightly rusted 914 for the track.