The subscription for Tivo is the same for the standard definition Tivo sold in Canada and the HD Tivos. There is no price difference if you are using the HD one or not. So no you are not paying for a functionality that you cannot use in Canada.
I meant the original cost of the unit, not the subscription. Surely part of the upfront cost of the unit goes to the cost of hardware. Although that will pale in comparison to the monthly sub fees that you will pay which is the one downside to TiVo.