This is an eye opener. A great frustration of buying online from the US is how many vendors will insist on using a courier when I would like them to use the post, which would (I assume) be cheaper.
Is your Post Office really hard to deal with? I am shocked that they have the right to open you package and see if the box you used might once have been sourced from them, even by someone else. What if I succeeded in getting someone to send this priority box to me in Australia and then relabelled it (covered the priority markings) and send something back in it? I have to pay Australian postage AND the recipient needs to pay US priority postage in receipt as well?
Sorry, this is mad. I can see that they cant be giving out free boxs but IMO if this is a problem they should keep the boxes behind the counter and only give them out to people who are purchasing a priorty sticker to put on them. That way, they get paid for the box. ONCE. I cannot see how they can claim rights over the box in perpetuity. I am not a litigious person but I would love to see this tested in court. There are certainly some jurisdictions where individuals would have property rights over the box once they received it.
Why dont they pre-print the boxes with the correct postage and just sell the box for the cost of priority postage? (This is what they do in several countries I have lived in- I didnt think it up all by myself, although I probably could have.)
I seriously dont get it. If you have two ways to stop people from stealing boxes from you would you chose (a) dont give out free boxes or (b) open every package that looks like it might be using a box that was once free, without having any idea whether priority postage was ever paid on it. And then chase them all up individually and in person and ask them to pay extra?