Here's how you measure whether the card really has that much value:
What does the victim now do? If he doesn't replace his card, but instead buys himself a nice overseas holiday or a second hand car it similar, we know the card isn't really worth $8,000.
Personally, I'd be surprised if he spent the $8,000 on a replacement card.
I don't know if that's enough of a measure.
There are many reasons to collect things, and many reasons to let go, too.
It's easy to think of a scenario where a collector sells an item for $8,000 and doesn't replace it but instead goes on holiday or whatever. (In a way, that's what it means for an item to "have" value.) Many of those perfectly valid scenarios would apply just as well to an insurance claim as to a sale.
Not as long as arbitrary monetary values are given to personal items in a civilization dominated by capitalism, wealth inequality, and vultures looking to cheat the system that failed them.
The card is not worth $8,000. Its worth is purely sentimental, after it was originally purchased for what, $0.50? As long as obsession over money exists, people will manufacture products at low monetary cost, sellers manipulate buyers with talk of rarity, people will pretend things are financially extremely valuable, and other people will seek to acquire it.