I would rarely pay more than 50 or so bucks for much of what this seller offers, although I did go much higher on a Choun Kiln gyokuro set that I was convinced was by Choun ... although I won't say if it is the age spec'd, but whatever.
Like someone said above, he seemingly has a never ending supply of "30ish year old" vintage pieces, often seemingly never used, or used so little that the pieces appear brand new.
I envision he has an endless warehouse filled with antiquiTeas like the warehouse at the very end of Indiana Jones Raiders of the Lost Ark.
Also, this can relate to an older Hagi topic and boxes (the topic regarding the "faked" boxes), this seller will buy bulk new Hagi very cheap, get the boxes himself, and allegedly sign the boxes. This is an obvious attempt to inflate the auction bidding. I have this info on good authority.
So who knows what else is going on there.