Well both ways, generally. 75$ is what Air Canada charged me for my extra duffel, both ways came to 150. I also decided to use my lunch allowance and purchased meals at the Airport totalling around 40$ over the period of two travel days. In addition if you require/are not supplied transit to the Airport/from the airport I you can claim your taxi/transit there.
Again, make sure you keep your receipts or you likely won't see your money again.