There is a simple problem you run into. Usage based billing only works in the following idea.
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-company charges $x for unlimited plans because their network costs are high due to a few people using a LOT of bandwidth.
-company switches to usage based billing. Charges less as high bandwidth users now pay what they owe vs low bandwidth uses paying the difference.
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However, this is not the reason for usage based billing in this instance.
Instead Bell, the backbone company was forced to charge ISPs on it's backbone an "at cost" rate, meaning they couldn't charge more than it cost them to run the line. This allows the ISP to determine what pricing plan they want, including usage based to reduce overall costs.
During this time, an ISP going to usage based billing can potentially have lower costs for other clients.
Now, Bell is charging it's original rate, along with an extra $1.12/GB over a low 60GB limit. This artificially raises the rates of the smaller ISPs that are on Bell's backbone as they were paying all of Bell's costs for those lines to begin with, and now have to pay even more. Meaning that the ISPs were likely already at the lowest amount they could charge, and have to now pay a gigantic extra fee for simply moderate usage.
I am short on time right now, but the quick and simple is this. Usage based billing only works when it's the company that deals directly with the customer that determines it, not the backbone. The backbone company getting to charge extra only raises rates for it's competitors.