After thinking about it, I realized that even though Google charges separately for Canadian data at $10/GB, I actually only pay for data used so in effect it is the same cost as in the US and my bill would still reflect only data used.
However, no one ever figured out why tethering did not work for me in Canada so I cancelled the service. I had high hopes for Fi but it let me down badly in Canada.
Also, I must have missed it when I researched Fi before I signed up, but calls in Canada are not unlimited like in the US. They are $0.20/minute unless you are on WiFi. I ended up being charged about $4 for my two calls FROM Google support while in Canada
I still think Fi is on to something and I'll be checking in from time to time to see if they straighten out the Canadian tethering thing.
Paul