The shipping calculators are not very accurate for UPS and FedEx. Usually way overpriced.
I shipped a large item (4 ft x 3 ft) and the calculator said 325.00. At the UPS drop center, it was 126.00.
I asked them about it, and he had no idea how the website calculates stuff. Everything is by dimensional weight now, not actual weight.
If it is a small Item, I just give an estimate that is close and if it's a couple bucks more I just pay it.
Large expensive items (over 1000.00) I usually charge a flat rate which covers half and I pay the difference.
Super expensive items I include shipping as a courtesy for buying such an expensive item.
If buyer wants exact actual, I just give an estimate I know will cover it and it is very easy to refund the difference if it is less.
I will say some sellers shipping has been so high it has nixed the deal. I like sellers who share the shipping costs with me when I buy something.