Recently, the postal rate went up. A customer from last summer who ordered a 24x36" print complained that the shipping went from $5.50 (last time) to $7.00 This time. The actual postage was $6.95. I do spend more time packing and shipping than actually printing:-).
Yes, printing on demand becomes way less attractive if one small print also has to be shipped. The more square meters and additional work per order is worth a reduction in price per square meter. P&P is always a separate cost on the invoice.
For shipping flat I use heavy corrugated carton pallet sheets (pads?) about 3.3x4 feet. Actually reused ones with an embossing of the round cans they carried before. Cut two lengthwise on the print width and length + 2" and glue them to a cross with simple wood glue + a weight on top. An extra sheet is cut to the print size + 2". Prints are packed in paper and that taped in the center of the cross. The extra sheet on the prints and the cross folded to a package. With the corrugation running in two directions the total becomes rigid. 2 Euro in packaging material, about 15 minutes work. 7 to 10 Euro for the postal service, depending on size and speed. Extra carton sheets etc for a bundle of prints or larger prints.
Met vriendelijke groet, Ernst
February 2017 update, 700+ inkjet media white spectral plots