Some sellers include shipping in the asking price. This is called Free Shipping.
Some sellers include part of the shipping in the asking price.
Some sellers choose the cheapest shipping service.
Some sellers want to have Delivery Confirmation and insurance.
Some US sellers use the Global Shipping Program which charges duty and sales tax up front.
Some sellers use couriers rather than the postal service.
Some sellers don't ship to Canada and what you are seeing is the US shipping cost.
When you compare prices, add the shipping cost to the asking price (or your maximum bid in auctions) and decide from that which is the best price.