I think if postage is listed on the auction this is what it costs,ie packing material,time etc.
However last month i won a item and postage was listed as £14.00
however when it arrived it was just stuffed in a empty box,no packing/bubble wrap and it only cost £3.20.
the box was all battered and squashed,so i was annoyed and asked the seller for a postage refund,he just fobbed me off for a few weeks,then i made a paypal claim.I then got my money back.I think that was out of order,if he had made some attempt to protect the parcel id have been happy.