I don't use Etsy for my Canada Post shipping - I use Canada Post's "Solutions for Small Business" which keeps the discounts in my pocket and builds a history with a crucial supplier (without relying on Etsy to decide what discount to pass on).
CP has 4 levels of discounts and they apply to International and Domestic shipments. The more you ship the greater the discount level.
I get better discounts from Canada Post than I do from Etsy now. It's a bit more work (you have to log in to CP and do shipments online there) but totally worth it.
Link here:
https://www.canadapost.ca/web/en/pages/smallbusiness/default.pageScroll down to the grey area to see the discounts.
Yo need to start at level one apparently but they'll check and upgrade (or downgrade) every quarter. Little pain for some gain depending on your volume.
Tif and Steve I feel your pain shipping rocks from the North :) Worse than shipping Books from the West!
Diane