Most sought audio gears

Everything,because its cool.

one might draw an inference that those items which are seldom available for sale are preferable to those which are available for sale.

I think it can be a lot like real estate, the best neighborhoods hardly ever have listings and they turn over quickly when they do....

Rarity has something to do with it, along with a good story. If some old guy, preferably near death, makes something out of exotic or rare parts that helps as well. And if their name ends in an O, like Kondo, Sugano or Shindo, well that's all the better. My little equation:

Rarity + fairy dust = most sought after

The question is too general and too ambiguous to be answerable. But depending on how "most sought" is defined, a good case could be made for Western Electric speaker drivers, tubes, and tube amplifiers from the 1930's. As to why, because they are extremely rare and, if in good condition, they are apparently extremely good.

Regards,
-- Al