T-Mobile has a new plan for a household celluar router they sell. It is priced similar to the way cable is priced.
For a lower offline cost, I have a Google Project Fi sim in my celluar gateway. It cost $10 per GB for the 1st 6GB, then it is free after that. If you exceed 30GB, you could be throttled. You can choose to pay to regain full speed.
Dave Anderson