I don't like that sellers can hide the amount of postage they paid for when they print labels at home using PayPal... I am too lazy to get out the scale and calculate on my own...
When I sold on Ebay I always listed "shipping & handling charges" My standard handling charge for most items was $2.00 This helped defray my costs for boxes, bubble wrap, packing tape, etc. Personally I used a lot of bubble wrap in wrapping stuff so it didn't break in shipment. I was always upset when I got something shipped to me thrown in a box with some crumpled newspaper. It wasn't my goal to make money on shipping, it was my goal to cover the true costs of packing & shipping.