USPS Priority Boxes

We bought a locker recently that had hundreds of flat USPS Priority boxes of different sizes.  They have come in handy for various reason but was wondering if there is any resale value considering you can get them for free for USPS.  BTW I really appreciate this community I was up late trolling some older post last night and it was great reading.

Definitely no resale value since as you said they are free at the post office. Probably even rules against it.