My aim is to neither make nor lose money on shipping.
I use the post office to send jewelry. A charge of $4 will cover the packing, postage, and insurance.
Unfortunately UPS makes it more difficult than ever to approximate shipping. For in-state shipping the rates and add-on rural fees have gone up so high that I have moved to using the post office. For out of state shipping I have to make an educated guess. A single piece of pottery will cost at least $15 to ship UPS, more if it is a larger piece or going out west.
I ship insured. I have a very good record with UPS. Damage is very rare except between Thanksgiving and Christmas, and unlikely even then. Always be sure to check your delivery promptly and if there is any damage save the packing material and notify UPS on your end right away.
My packing fee is based on the size package needs to be which depends on shape and size of piece. Platters and bowls take more space than pitchers/vases as they are more vulnerable. Minimum packing fee is $4 for a single piece. It can be as much as $20 for a large piece.