The paper he cites, Waldfogel's "The Deadweight Loss of Christmas" omits one of the most valuable results of gift exchange. Namely, it only considers the intrinsic value of the object give, and not any goodwill or pleasant feelings that the mere act of giving and receiving itself provides.
In other words, by focusing purely on the material value of the object given, the paper systematically undervalues the benefits of the entire act itself.
Yes, and in particular, the deadweight loss has value because it is deadweight loss. "I paid $100 to ship this $10 thing that you could have gotten yourself on Amazon for $10" is another (admittedly strange) way to say, "I care about you so much that you having $10 is worth $110 to me."
That sounds more like “I care about you having this $10 thing more than you having $110, $10 of which you could use to buy that thing while still having $100 leftover.”
In other words, by focusing purely on the material value of the object given, the paper systematically undervalues the benefits of the entire act itself.
Waldfogel himself noted this in a follow up.