Not too hard to figure out that it was a Canadian deal. I have been bitten in the butt by Canadian shipping a couple of times. Mostly because I am a typical American and assume everyone is American. So I have said things like "I can do that for $35 shipped." Only to find out it was Canadian shipping and I spent almost all of the money from the sale on the shipping.
To me, it is incumbent upon both parties to comunicate. But ultimately, as a Seller, you have to live by the terms of what you said you were going to do, regardless of whether you take it in the can on shipping costs. And both of the Canadians were quick to remind me of what I had committed to when I asked if they could see their way clear to splitting the difference.
I think the same thing goes for buyers, and if you did not deal with the shipping up front, then it really kind of boils down to it being whatever it is. Sucks, but I don't see any other rational resolution.