Unless the slab was somehow manipulated, You crack it, it's yours until you sell it!
Sellers risk much on eBay. This is why I'll never sell there.
At one point, wasn't the top sale recorded for a comic book sale, made through eBay? Maybe it was just a certain copy, and not the record.. A Sup book??
With FeeBay taking a small portion of sellers fees compared to big time trusted auction houses that make the lions share of the profit, it makes sense to many sellers to sell more expensive books on the ugly & terribly skewed platform. I've not sold on eBay, and have bought comics (once I knew it was local and we could do a transaction in person.) Too many shady folks for me, among the trusted sellers.