I live in Calgary and do most of my fabric shopping on-line. I have ordered many many times through the US quilt shops and only once have had to pay duty and it was minimal and I still saved. I have even ordered a box of quilt batting, never paid duty and still came out about $80 in the black. When I figure in the shipping and exchange, I'm still ahead of the game. I have some favorite shops that I frequently check on line.
I was in Montana doing a shop hop of my own a couple of weekends ago. I was slightly over my limit, claimed it coming across the border..."Thank, have a good day." The prices in the US are at least 1/2 of what is charged here. I now have a account set up with a shipping outlet near the border and can have my fabrics etc. shipped there for a very minimal fee. This takes advantage of some of the "free shipping" offered by some shops. I still go occasionally to my LQSs (though one shop is higher priced that the others in town)but usually keep my purchases to a minimum, or something I need right away, or if they are having a big sale. When I visit family in Ontario, I usually check out the shops there, but the prices are pretyy much the same.