Depends on the size and weight of the package.
In Dinkins' case, his package is big and the weight is heavy.
But seriously, I sent a DVD, nothing else with it just a disc, to UK for $10 using registered mail (had to be signed for and all that shit). $15 for a (ass) hat is a bit high. Your problem is that the guy is likely charging shipping and handling. They can make the "handling" fee anything they like and your fucked into paying it.
You probably should have emailed the seller before bidding to find out what shipping is.
I know that if I put up an auction and say no out of US'rs are to bid, and the winner is out of the US and didn't contact me, I'll charge them a nice handling fee.