It is up to individual sellers how they handle the postage on their listings and as long as nobody is contravening ebay policy by selling items worth $99 for $1 with $98 postage ebay should not have any input.

I choose to offer free postage on the majority of my BIN items because I know exactly what the total cost is going to be and can factor the extra fvf into the total, for my auction items I quote postage with a very reasonable packaging and handling charge and I have never had a buyer complain and my postage cost stars are at 5 or 4.9 on all my selling ids.