Milance
If you want more legroom in air transat well you can pay little bit extra, and one way is more expensive than return, and alos it is high season , most of the people they booked their flight from January , I can see every day prices higher than 1800 for one way tickets ,
I am a travel agent and every day is harder and harder to find a cheap price, longer you are waiting more expensive flights are.
Air transat is not bad as you are saying , I have clients and also myself travelled with Air transat I upgraded my seats , and service was not bad, better than air Serbia ( or Ex Jat )