I recently brought an item of clothing for DD that had £5.60 postage. I thought that was a bit high at the time of bidding and won the item for £6.00 (plus the postage).
When it arrived it had only cost £2.60 and was in an old, reused, very tatty Jiffy bag. Although I knew the postage cost before bidding I'm a bit annoyed at the huge disparity, especially as I paid a very good price for the item (Joules cardigan, a little more worn than the description had led me to believe as well).
If it had been sent first class, in brand new packaging I wouldn't have minded.
Would you ask the seller for a partial postage refund?