"and make their profit on the Internet because it costs so little to provide once the basic cable plant is built."
That's some big hand waving, because laying the cable costs a fortune, and takes many years to recoup the cost which is why there is so few are competing for this "super profitable" business.
Without knowing the specific numbers, I'm pretty comfortable saying that the costs to an ISP to get the bits all the way until they reach the peering point is much less than the costs to an ISP to continually upgrade their network.
That's some big hand waving, because laying the cable costs a fortune, and takes many years to recoup the cost which is why there is so few are competing for this "super profitable" business.