Earlier quoted context omitted.
The problem with those private keys being sold off-net is that the buyer can never be sure the seller deleted every copy. Who would take that risk? And who would buy it and not use any of it? Even if the value tanks it'll still be a ton of money.
Correct, with all single signer ownership you can never be sure how many custodians there are So you’re right and we would never be able to prove that any amount has changed hands or not, only assume that others wouldn't take the risk
Sure, it is a network based on trust. But the whole idea of bitcoin's principle of trust is that you trust the majority of an entire community.
By making a deal with a single party for their wallet credentials you have to trust only the seller. One single party. In a shady deal involving a fortune.
And like I said, who would spend obviously phenomenal amounts on something and then never even touch it? When the buyer could simply move that trust from one party to the community simply by transferring the balance to a new wallet.
Of course the ripples in bitcoin's value would be unprecedented. But the buyer would hold so much of it that one way or another they would be extremely rich.
I'm not really talking about the sharing of keys in general by the way. Just about the thought of Satoshi's genesis wallet keys being sold this way.