I think that you guys are seeing it from the side of a collector buying, which is not the case.
The intent is to buy, then on sell for profit.
At a minimum, they'd be looking at doubling what they paid. For them to do their job properly, they need to pay as little as possible.
The 'labour' for a non collector would be fairly time consuming if those toys were all loose like that. You'd need to identify them all, work out if there are any bits damaged, and then try to put every weapon on the correct toy.

If the guy selling was serious, then his toys would be on eBay, not trying to get market value on his toys from a dealer.