Basically it caps off at $60 after 6GB, is free up to 15GB, and then throttles.
That's pretty great pricing especially considering it works anywhere in the world.
Disclaimer: I am a Google employee, Fi customer outside of work, don't work on Fi.
I guess when I signed up for Fi I imagined myself travelling more outside of North America.
If they're literally charging double compared to the domestic competition, it's pretty outrageous.
Google Fi is also flexible in that you don't have to spend $80 a month if you are using less. When I don't have to do a bunch of tethering for work, I usually spend $30 - $40 a month total.
Thus Google Fi cheaper for a variety of use cases. Different plans/carriers are cheaper for different use cases. Just because a carrier other than Google Fi is cheaper for your use case doesn't make Google Fi outrageously expensive.