What are the speakers you very rarely find in the Used market(Audiogon or Anywhere)?

Sony SS-AR1. Even more rare are SS-AR2 speakers. 

U-Vola seem to be pretty rare https://www.ebay.com/itm/323737117992

I mentioned that Sonus Faber Extremas rarely come up for sale. I dropped in to LMC Stereo in Scottsdale, AZ yesterday and there they were. They were around $10K when introduced in the 90’s. The new version are $70K (new, $65K used). They are gorgeous, but the price is shocking (to me, anyway).

ACI Jaguar 2000, ACI Emeralds. I have the Emeralds, heard the Jaguars are awesome!

Windmilldad: I own ML 13a. (I can speak from experience having been an audiophile for 5 decades.) They were very good speakers when matched with reputable amps and preamps. A year ago I took it to the next level and went with Don Sachs tube preamp and Krell’s 575 XD mono. Now they’re a great speaker, I can’t imagine better SQ. Two important items when working with the 13a, the amp needs plenty of power and the preamp should be tubes. Enjoy.