I tried using “live postage rates” on my shop and they were never right. I had a LOT of packages returned as “not enough postage”, so I went to flat rates. I always do my best to refund any shipping not used, as in the case of a small $3 order of a few strips of 6mm troops does not require an $8.35 priority box, so a padded envelope that totals $2.50 in cost and shipping has the rest refunded.
I do tend to eat the cost on overseas shipping quite often, as the rates are totally diverse and seem to fluctuate daily, even to different places within England itself from the US. It blows my mind that I can send a package of the same size and weight to Durham, Plymouth and London as well as to Australia and the one to London will cost more than any of the other 3, consistently.
"I saw this in a cartoon once, but I'm pretty sure I can do it..."