Shipping knitted and bulky items

Several people have been asking me when I plan on opening an Etsy shop, or otherwise selling online. My answer is usually along the lines of "Whenever Canada Post drops their shipping costs".
To ship anything thicker than an envelope within Canada, it can cost as much as $13. That same package going to the US only costs about $6. That is where I am very confused. It costs less to send a package across an international border than it does to go to the other side of my own country.
I have considered crossing the border once a week to ship anything that would be cheaper to do that way. This would quickly become expensive and time consuming. Not to mention, I may have to pay duty to bring everything across.

How do you ship your items without costing the buyer an arm and a leg? I am trying to figure out how to ship my hats and scarves for less than $13.