The salary adjustment seems in line with what I have seen and heard from others who made transfers with my past employer especially if you are in the bay area and are planning to move to the GTA. Also, 200K is not that uncommon anymore in Canada. Even at that range, employers are probably easily making a 20% cost reduction when 200K USD becomes 200K CAD 
Of course, base salaries won’t be that high but your total comp could definitely go up much higher than 200K for tech roles depending on your level, the company etc. Especially, if there’s equity involved, then we are talking about RSUs in USD so that adds to it as well.
There’s a thread on cost of living comparison between bay area and GTA here. That might throw some light.