I am in no way claiming that the person is lying, I in 10 years of working with amazon never met such a thing and for me it is jusy very surprising moment.
Also if you sell something on amazon/ebay , I would advise you to use such services as labels.vs (all functions open after registration), here you can buy cheap usps shipping labels for 4-6$.
Also for sending abroad use such services as sendle or pirateship (delivery is 2-2.5 times cheaper than directly through usps or ups).