I charge the flat rate for priority mail regardless of the actual charge. For UPS 2 day its anywhere from 25 to 28 dollars for up to 2 pounds. 3 pounds and over, it starts going up. If you are ordering plants on wood, each piece is between 1 and two pounds. Depending on the size of the wood and the size of the order, I may have to use a larger box than my standard 12x8x6. That also makes the shipping charge go up. UPS goes by the dimension of the box and the actual weight. The rate is slightly lower when going to a legitimate business address than residential. Usually about a 2 dollar difference. They will not consider a home business a business address.
I strongly suggest spending an extra 3 dollars to have the plants in a thermal insulated bag and cold pack, regardless of what shipping method you choose. Plants are guaranteed for UPS ONLY. No guarantee on plants for priority mail. The thermal bag will help.