The DoorDash pizza arbitrage comparison is apt. Both cases expose the same fundamental thing: venture-subsidised pricing creates artificial market conditions that clever people will exploit.

What I find interesting is how long these windows stay open. You'd think someone at Stamps.com or UPS would notice the pricing anomaly, but large organisations are often too siloed. The team setting international rates probably doesn't talk to whoever monitors small parcel economics.

The author mentions making a few hundred dollars - but the real question is scalability. At what volume does this become attractive enough for the postal services to close the loophole? There's probably a sweet spot between "not worth their attention" and "actually profitable."

The USPS have been on the receiving end of it themselves back in 1916 when someone mailed a building:

https://postalmuseum.si.edu/object/npm_2022.2007.1

https://about.usps.com/who-we-are/postal-history/bank-of-ver...