When I BUY from Ebay I always check the shipping and see if combined with the price I want to pay the total or not.
When I SELL I LIST the shipping, there is no guessing, no surprises ect.
Either as a buyer or seller you know BEFORE you bid what the shipping will be.
So if you bid you are in essence AGREEING to the shipping, so why should buyers be able to leave negative numbers for the shipping charges???
If you don’t agree with the shipping DON’T BID!!!!!