Frankly, what providers define as “usage-based billing” isn’t really usage-based at all. It’s simply a double-tiered pricing scheme. Consumers already pay for broadband service based on speed, which informally includes a usage limit of sorts — your maximum amount of consumption is governed by the speed of the connection you purchase. Not satisfied with the enormous profits already earned selling broadband that way, some companies want to monetize Internet use by inserting usage limits or inserting a new tier of service based on usage allowances, which generally increase with higher-priced levels of service.
Source