I was just checking USPS shipping and looks like Priority Mail is only $4.60 up to 1lb, then over that it jumps to $7.50. (Parcel Post is a bit less) That's from East Coast to West - VA to Calif. You can pickup a 1lb kitchen scale at the Dollar Store that'll help calculate the total shipping weight. Pads are very light + a box/envelope, can calculate how many pads you can ship for 1lb or less.
USPS Postage Calculator