You can save the images when done. They are too expensive to get done (well postage is) and I also don't have commercial rights for images or logo so they are for personal amusement only. Although I have a mate heading state side so may get them done and sent to him.
As a NRL collector I don't know much about COMC but did have a look at "mymailbox" and yeah could save a few dollars but have no idea what the size / weight of the package would be to calculate it exactly.