What used speakers raraely come up for sale

Ridge Street Audio - Sasson - An incredibly good stand-mount speaker that was probably under-priced new @ $10K when it was on the market. I don't know how many Robert sold, but you never see them for sale anymore. I heard them in 3 different settings and all were fantastic.

spendor sp100r ,spendor sp100r2

Any of the Apogee models.

@cakids,
Agreed on the AP Scorpios.  I owned a pair in ebony for a while and the were one of the most attractive speakers I've seen.  Plus they sounded great.  A real bargain for high end sound and aesthetics if you can find them used.

Here's a super rare speaker that would be simply killer to pick up used:

Waveform Mach Solo.

That was the slightly smaller, passive version of the famous Waveform Mach 17 speakers by John Otvos.   The Mach 17s were one of the most amazing sounding speakers I've ever heard and earned tons of raves.  But they were large, somewhat odd looking with the "egg" module on top, and required 3 amplifiers.

So Otvos came out with that Mach Solo speaker, which was actually more gracefully proportioned and came with John's absolutely top notch wood work, with exotic veneers.   I had one in my place for a while and it was almost museum quality and sounded awesome.

But you almost NEVER see them come up for sale, both because not a lot were sold and also, I'm sure, no one would want to part with theirs.

The only used pair I've ever seen came up in the last few years, where Otvos sold off his own pair.