It cost me...yes, I have to PAY for the bandwidth my customers use. I cap them at 30 GB per month, its in my contract. If you exceed 2 GB per 24-hours, I throttle your connection, its in my contract. If you don't like it, don't sign the contract.
This is a network neutral method of managing bandwidth. I don't see an issue with it as long as you are not granted a right of way which creates a monopoly in your service area.