Possibly the worst I’ve ever encountered here in the U.K. was during the 90s.
He had a two-tier system, ‘Fine’ and ‘Near Mint’, where he’d take the Fine or Near Mint price for the book from the British Price Guide and half it.
Except…
’Fine’ condition was anything that looked a bit like a rag, VG, G or even less, (I got sent some really crappy-looking Marvel horror mags) and ‘Near Mint’ was anything which superficially looked in nice shape, possibly what we’d call Fine to Very Fine or better.
So, the pricing wasn’t quite as generous as it sounded.
Compounding this was a lot of clearly superficial cover grading going on. I bought a Son of Satan 1 which looked really nice externally, but, the usual amateur mistake, no Marvel Value Stamp inside. I wrote back, possibly returned the copy, can’t remember as it’s 3 decades ago, and never heard anything more.
As I said, incompetent amateur hour grading, to be polite, with all the finesse of a scrap metal dealer, which I believe was one of his other interests.