You may have also noticed that the Canadian dollar price is an approximation. It's likely going to be a bit higher than that because of how payment processing handles currency exchange.
My guess is that it works this way because when the item is found in search results, that approximate conversion to Canadian dollars is shown to make it a little easier to compare prices, but once you bring up the listing page the US dollar price is more prominent to underscore the fact that you're dealing with a currency that's not Canadian dollars for this particular listing.
