Postage On Things Other Than Envelopes / Postcards

I wonder how much postage it takes to send your kids to summer camp?

I don't have an example, but does anyone remember the 16mm educational films that you used to rent through the mail for schools, churches and other non-profit organizations? Before the plastic canisters, they were shipped in a formed box with web strapping to secure the parcel and then mailed to the recipient with a postcard insert where the address would appear and where you'd apply the postage. The problem was that the postage often exceeded the space on the small postcard, resulting in stamps being pasted all over the container. Nice, often high value stamps, with handstamp postmarks were often the case, however, because they were on the box that had to be re-used to send the rented movies back, there was no convenient way to remove the stamps without damaging either the stamps or the mailing box.