Hi

I'm trying to maximize miles by creatively routing YYZ-SFO. ITA Travel quotes $250 (US) for YYZ-YUL-YVR-SFO. However, when I try to select a multi-city itinerary on the AC website, and pick my flights manually, it adds up a separate fare for each segment, and the total at the end comes up to something like $860! Is there something I'm missing here?

Thanks