Here are a few things I see wrong with this.
1) They are selling a $150 Dayton ADA-150 for $1,950 with the dubious claim of "upgraded" parts.
2) They are selling a Behringer A500 which is normally $200 for $3,500 again with the claim that they "asked them [the manufacturers] to make some modifications" to "bring them all the way up to high-end specifications".
3) To name a company Linn Audio and sell stereo gear when there is already a well-established audio company by that name is certainly infringement.
Even if you completely ignore the questionable sonic qualities of their products, it seems to me that these facts amount to fraud.
I would contend that, while Audiogon is not liable for the products, claims, etc. of their advertisers, they do have a responsibility to avoid supporting organizations whose intent is to take advantage of Audiogon members.