I booked my tickets in March so I got the early bird offer around HKD8000/person (Air Canada), I think if you book now, it will be around HKD12500. Maybe you can plan for next summer, Air Canada usually has early bird offer around Feb/Mar every year.
Air Canada is better than Cathay. Both are non-stop flight to Toronto but AC takes ~15hours, CX ~17hours. You have to take 2 more hours with CX. Besides, the seats of CX is smaller.
AC's timing is better. Leaving HK at ~3pm, arriving ~5pm.
My friend got the early bird last Dec, its only ~$6500. My ticket is ~$9X00, issued in May. :-( :-( :-(