alt Hacker Newsa large part of the value of secondhand stuff is in the box and packaging, assuming those nice boxes in the image were from his collection - those are a little more fragile than the Lego pieces themselves.
Edit: wait, the whole collection was sealed and new in box. Yea, just water damage to those boxes would cut the value by at least 10%. Collectors are picky as shit.
They were sealed in box? Yeah you'd be right that damage would be easy and could significantly reduce the value.
I didn't realize people bought Lego to leave in the box. But I guess I shouldn't be surprised because it's a common thing for collectors to do in other hobbies.