C and I have Google Fi, so we pay $30/month for 1GB of data, and everything over that we pay at the same rate, though we've never gone over. The price of calls and sms depends on the country, sometimes it's free, sometimes it's cheap, sometimes it's more costly, though we typically call on wifi if we need to which is free. But having seamless service in almost every country is pretty swell. We've been to 9 countries with it so far, and it's only not had service in one. ^^ Though, that's just data - wifi always works, which is a lot of what we use anyways.
I <3 Google Fi.