I only see a few of them listed on Audiogon by private sellers. Those few have been listed for less than 3 weeks.
As you mentioned, they were positively reviewed by TAS along with an Odyssey amp and another, I believe it was Bryston. This certainly lends a bit of extra credibility to anyone selling these items and that's why I don't often see them for sale.
Of course, the number for sale is related to the number originally purchased, the general availability of the product in the market and the number of people wanting to sell theirs.
If I were ready to make changes to my system that would be one of the first items I would likely purchase.
I probably haven't looked into seriously buying one so I haven't noticed the same trend as you have, in fact, I would have guessed that the opposite is true.
