Price difference between Canada and USA

I have been looking to order a new pair of earbuds and found a good deal on amazon, only to discover I was on the american site. Ok, so I switch over to the Canadian site to find the $13 earbuds have jumped to $30 Canadian! The difference in our dollar isn't that substantial, however I'm not sure how much extra it costs to ship across the border. Does anyone know why this price difference is so much?