"If it's a print that you value then flat is the only way."
Well, not exactly. Kind of tough to ship a 40 x 60 inch print flat. Rolling is fine if you do it correctly to protect the print surface. I cover each print with tissue paper, then slide into a large flat plastic bag. I roll the print around a tube (protects from being crushed or kinked), then cover with bubble wrap and then either place into a long box or into another, larger tube. This is for prints 24" x 36" and larger (with smaller ones they only go into a single tube, but still with the tissue paper and plastic bag for protection of the print surface). The presentation is better with a flat-shipped print for sure, but sometimes the reality of the situation (size of the print) dictates a tube. The rolls do tend to roll off onto the floor and get manhandled quite a bit since they won't hold still during the shipping process, which is one reason I often use a long box for the outside container since they won't roll. I've had both very sturdy tubes and flat packages destroyed by the shipping services (generally it is easier for them to bend a flat then a thick tube, so if you ship flat be sure to put some really stiff boards in there). And for some reason the post office likes to bend everything in half these days (I ship the larger prints UPS - so I can collect $100 if they smash/bend one - smaller ones via post office).
One thing to keep in mind when comparing prices at the Yazoo site that was noted above is that their prices include shipping (looks like they will ship to Canada, although for a different price). The shipping costs can often be as much or even more than the cost of the tubes so you need to factor this in when looking at other vendors.
Make sure prints that you sell include the costs for the packaging and shipping, which can add up to quite a bit for larger prints if you do it correctly, and why do it any other way...
Tim Ernst in Arkansaswww.Cloudland.net