[megaman821]

Thanks for the links. The problem with your profit margin calculation is it assumes 100% of consumer traffic is going out to a different network and that Tier 1 ISPs have arrangements where incoming and outgoing traffic on their networks cancel out so they usually end up paying each other very little money.

[JumpCrisscross]

Yup, that's why I labelled it as a minimum profit margin and parenthetically noted that the cost per Mbps used is probably higher than reality.