Actually, billing based on number of bytes transferred has absolutely no relation to the ISP&#x27;s cost of providing the service.  ISPs have a fixed amount of bandwidth to various upstream ISPs.  If customers exceed that at certain times of the day (or always), it costs the ISP money to upgrade their connectivity.  If the customers aren&#x27;t exceeding that capacity, there&#x27;s no additional incremental cost.  So if all your customers check email at 9am, that could be more expensive than a bunch of people who are constantly using their entire 1Gbps to run Bittorrent.<p>Similarly, that&#x27;s why Netflix and Youtube struggle to load their 5Mbps video streams, while Bittorrent works fine.  Bittorrent will simply not get any data from peers whose routes take the packets through the congested link, but use all the others.  If there&#x27;s only one route to a service, that&#x27;s more likely to hit congestion.<p>Anyway, if ISPs want to charge for bits transferred, they&#x27;d better be upgrading their peering links and charging you based on how you&#x27;re increasing their costs.  Otherwise they&#x27;re just charging you Because They Can, which is the real reason behind data caps.  (What are you going to do, switch to their competitor?)