they must have had chimpanzees doing their inventory.
In this auction- Old $$$$ Million Dollar Comic Book Collection they say that
"After a couple of years of work whenever time allowed, we have NOT come close to finishing, having done probably less than 20% of the comics. We have managed however to get through over 7,000 of the books "
2 years to inventory 7,000 books? That's like 10 books a day. Even accepting "whenever time allowed" as being prohibitive, that's a snail's pace.
It's been a while since I've gone through a large volume of books, but I'm pretty sure I could inventory 7,000 comics in about a week. They should have hired me.