@ik345 I never thought about cost to ship a tube, but USPS considers tubes as boxes, so probably not any less expensive. Unless one of their tubes for Priority Express Mail is used, in which case the rate is, these days, astronomical.
One thing I noticed when checking it out is that the USPS “tube” is prism shaped.
I did some testing and found I could roll a full sheet of cold pressed 300# paper into a 4″ diameter tube, but that was pushing it, so a minimum of a 6″ tube would be required.