I dealt with him once, when I ran out of all other options trying to find a Mac Plus keyboard.
The keyboard was ultimately $15 + $10 shipping for one with uneven fading.
When I mentioned I was looking for a SCSI to Ethernet adapter, but that I currently was a high bidder for one on eBay, his response was "I don't compete with eBay." and a link to his page where he listed some adapters and wanted some outrageous prices for them.
Then I inquired about getting an old Apple HD SC 20 case to stick under my Mac Plus. He had one listed as "Very Faded" for $20. When I asked about that, he replies back and says that one is gone and links to his page explaining the cases he has. He jacked up the price of the same "Very Faded" case to $29 and the prices of all the other cases. I told him I was no longer interested in paying $9 more for the case that was only $20 a day ago. He did discount the price of the keyboard by $4 though (from $19).
So I had a somewhat mixed experience with Herb.
I would say he is getting his stuff from schools or recyclers like I usually do. It looks like he parts off anything that's yellowed.