>the high cost and useless-ness of the gift are a feature not a bug! The burning of significant amount of wealth is a costly signal of commitment to the receiver.
No, they're really different. Just because the sunk cost fallacy has something to do with spending money doesn't mean it applies whenever money is spent in an unwise way.
But buying a wedding ring is not only about showing off, it is an old method of psychological trickery that is supposed to make relationships and marriage more durable.
It used to be "sunk cost" for a man, since until recently it was expected that if you break the engagement your ex-fiance would keep the ring (right now in most of the states law require it to be returned). Expensive wedding party is another sunk cost.
>> right now in most of the states law require it to be returned
Is this true? That would be very surprising, as it is essentially a gift, or at the very least, joint property subject to divorce adjudication like anything else.
So basically... proof of work?