Ok, but why should the buyer take the risk to lose twice the amount of coins, not receiving goods AND being extorted by the seller afterwards? As buyer I would not take that risk since we would not at the same risk levels then.
...the problem is that the collateral might be enough motivation for the scammer to force the victim to concede.
It is like in trading of cryptos, you will never lose until you sell cheaper than bought, even if the current asset price is lower than when you bought it.
The beauty of this scheme is that
without your wish nobody can scam you, but
the scammer will lose his own money. And only you, by your own hands, can return to the scammer his money plus give him your own. If you are considering such a possibility, just do it before the deal, you will win a lot of free time.
Which I think is the general problem with your plan. It's risky for both sides.
Exactly! But it is not a problem, it is the foundation of the scheme, a good motivator for the both parties to be honest each with other.