Seller is asking me for extra money for shipping after I paid the price that was asked for.

I won an auction and paid that price for the item plus the shipping listed for my country. About five minutes afterwards I got a message from the seller saying he put the wrong shipping details down and that I paid economic shipping price for my country even though it was listed as priority. He then goes on to say that we would require an extra amount to get the priority shipping even though it was listed as that.