Yes, along geographic lines. I understand that a 5 kilogram art book is going to cost more than a paperback. I accept that, and I can factor that into my pricing of the item. I had somebody buy a $4.99 paperback from me. They were living in a rural community in Alberta. It would have cost me $15 to ship it to them. What do I say? I'm sorry, but Canada Post doesn't think you get to participate in e-commerce? There's no cheaper way to send it.
You can add on top of that something that I failed to mention earlier, which is the fact that Canada Post is not bothering to collect duty on shipments over $200. The shipping advantage is combined with the fact that they don't have to charge HST if they are based outside of the country. It's almost as if they are out to get you. I just don't understand it. Only Canadians would set up a system that disadvantages their own sellers. It's the ultimate self-deprecating Canadian thing to do.