For clarity, when most Canadian's say "Quebec" they mean the province, when they mean the city they say "Quebec City". Just like the difference between NY and NYC.
Porter has a seat sale on right now until June 18th, $79 one way from Toronto City Centre to Quebec City.
Now, turn that into a round trip for two people, add taxes and surcharges and you're still going to be somewhere close to 400 clams or more.