I've only bought one manual from their website, it was a good quality copy, can't remember how much it was. My last enquiry about a Wayne Kerr manual never got a response
Which made me wonder if they had sold the originals on ebay.
Prices are all over the place, think it depends on supply & demand as with anything else. Your 5½ digit SE labs DVM wouldn't have sold as many units as a typical 3½ DVM used by a service shop/department and hence not many will be about.
David