If you decide to ship your prints rolled-up, please ignore my post. Also, your needs may be different to mine, but when I ship my prints (mounted, unframed) I "build" a case from corrugated cardboard sheets for them, each time. It is easy and pretty quick.
I take a stack of larger-size (maybe 26x30" in your case) brown, double-wall corrugated cardboard sheets, each about 8 mm thick, and each having its corrugation ("flute direction") at 90 degrees to the other one. In other words, I have two supplies of those, one corrugated lengthwise, the other widthwise, and the resulting stack is made from "opposing" ones. 1–3 sheets will become the top and bottom of the stack (1–2 for single print shipping, 2–3 for larger packs). Now, I cut an opening, using my mat cutter, in the remaining sheets, which will become the middle ones in the stack, the ones that will hold the prints. That opening is just slightly larger than the mounted prints.
If your prints are unmounted, you may want to consider including sheets of mountboard or foamcore to secure them. When shipping prints for framing, I add foamcore between prints, to further protect them, and to ensure it has my stamp on the back.
Each print gets wrapped in oversize, virgin-grade, heavy-duty polyethylene slip bag, and either it gets sealed, or simply folded and sticky-taped. Bagged print(s) lie in the openings in the cardboard sheets—in a way, the print is now in place of the piece of cardboard that has been removed earlier, and the board becomes a "frame" around the bagged print. The sheets get stuck to each other using double-sided tape, and/or with brown packing tape. Once the stack has been sealed, the whole lot gets wrapped in brown packing paper, and further sealed with more tape.
This creates a surprisingly light yet pretty strong package, one which has survived long international journeys.
I give credit to Anne Larsen and John Sexton for showing me their approach to print shipping and packaging, which I have only slightly modified (cross-wise interleaved corrugation) following a consultation with a local manufacturer of cardboard packaging, where I get the sheets from.