It just seems to be some distributor ripping Canadians off. I buy a bunch of parts for a variety of small equipment, as well as my trucks, and for some brands, pricing will be roughly the same, adjusting for currency, between retail price in the two countries, but for other brands, but similar parts, it will be 30+% more to buy it in Canada.
amazon canada is similar, some stuff is priced about the same, other stuff is just stupid priced.
I make a point of planning ahead, to buy stuff in bigger orders out of the states, so shipping is spread out over more parts, but I find it doesn't take many parts for savings to exceed the cost of shipping, generally I find about $100 of parts I'll be ahead.