I know it doesnt cost a penny to go from canada to US... I have done it several times ... all you need to do is apply for a new title in the states($20) I dont know what Canada charges you? I dont think you should have to pay a dime. just re register the vehicle. you will obviously have to pay whatever U.S. taxes. (city, state,fed) whatever applies.
Importing a car into Canada from the US?? There's duty (I think), PST, and GST. Therefore, there's no way you can get away with those items.....Since you're paying the taxes anyway, might as well get it in Canada.