In the existing payment market you have a seller with no stake and have to correct for it by drafting the payment processor to post a stake instead. Then if the seller doesn't send the product (or sometimes even if they do), the buyer makes a claim with the payment processor and the payment processor is stuck refunding it because the alternative is having a larger cost imposed on them by the government. Then they try to mitigate the loss by not paying the seller, if they can.

This is just unnecessary indirection when the seller posts a stake instead. If the seller has $200 on the line over a $100 value item, they're going to deliver it because the alternative is a $100 net loss. It's the same reason the payment processor refunds your money -- because the alternative is worse for them.

The buyer doesn't actually lose the extra $50, they just sit on it until the seller makes good, which happens eventually because the seller's alternative is worse. The end result of MAD isn't that everybody gets nuked, it's that nobody does.