A Propstore COA has an indirect monetary value, as without it there are less people willing to buy a prop, (thus lowering the potential resale value). There are replica makers out there that try to copy props to the smallest detail, so a COA in essence proofs the item is the auction item.
That's a fair point. I think a lot of people assign a lot of value to a COA, believing that it ensures that item is authentic. Which is how they are presented, to the point where even COAs are being faked, along with holographic stickers and the like.
Except that they don't, in general, warrant any sort of authenticity. There are very few COAs in the collectibles world that are searchable by serial number that provide sufficient information to determine if the COA and the item are both authentic, sports cards, coins and comics are the notable exemption.
Even in those cases, where you can search the database and compare, I'm pretty sure that the COA doesn't imply any sort of liability if they are wrong about the item being authentic. In other words, if they are wrong, it sucks to be you! I've heard of them refunding grading fees on cards and such when the item is later determined to be fake, but that's about it.
If COAs were really an important item that adds true value to an item, wouldn't all the major auction houses, like Christie's and Phillips, be doing them?
As it is, we currently rely on the honesty and integrity of the auction house selling the item, and it is in their best interest to be right. By and large, they usually are. The whole dog and pony show about issuing a replacement COA to the person WHO JUST BOUGHT the items is just... inane. All 4 jackets were on one COA, and he asked for a COA for each one. All perfectly reasonable. To me, it's not just that they don't want to issue a replacement COA, the unreasonableness of the how and the why are beyond me.
If I lose the COA in a house fire, will Propstore refuse to let me consign an item? I think not.