Earlier quoted context omitted.
When an ISP leases bandwidth to a customer, they must reserve some amount out of their total available. They may reserve the full amount they have leased, or they may reserve some portion of it. Either way, the reserve is finite and proportional to the actual total bandwidth (the proportion may be 1:1, which is the simplest, but the proportion does not matter for this discussion). The marginal cost of provisioning me…
For residential service, there is no reason to expect a 1:1 reservation. This would be extremely wasteful. The exact number is not relevant, but residential bandwidth is oversold as a matter of course. Talking about capex and aggregate costs also seems to be drifting from the main theme here: whatever it costs to double the network's capacity is going to be pretty circumstantial, and not directly relevant to the topi…
We're talking about average internet performance in a nation. This entire thread was kicked off by a comment about Akamai indicating the US as a whole has faster broadband than e.g. Germany.
The cost to wire up the US with an average speed of 2x that of Germany is absolutely an influencing factor in the cost of bandwidth to a consumer. We are talking about performance, not widgets. To double the performance of a nation's network from p to 2p, it is not unreasonable to expect that the cost is greater than double or greater than 3x the cost of performance p.
But, if you want to proceed from an analysis of marginal cost, we can do that as well. ISPs do not fit the model you are using.
Marginal cost for something like an ISP is not a single number. There may be 10,000 consumers with a marginal cost near 0. Then customer 10,001 may have a marginal cost that is "install a new backhaul to the network backbone and extra 10G or 100G routing equipment to serve your neighborhood". Obviously customer 10,001 doesn't get stuck with a bill of $100Ks to be added to the network.
You are attempting to pigeonhole an ISP into a model that assumes a single, flat fixed cost and (effectively) unlimited production of a good at a low marginal cost. That is not the industry we are in.
The fixed costs of an ISP are a stepwise function, not a constant. You cannot model an ISP effectively with an assumption of constant fixed costs.
All other things being equal, the marginal cost of a given customer is / N, where N is the number of customers that can be served before the ISP has to install new routing hardware, or in the unhappy path lay new wire.
Now, it is obvious that I have simplified things above. ISPs do not build infra for N customers, then wait for customer N+1 to build out the infra for the next N customers. ISPs invest in their infra in long planning cycles. They cannot effectively build out in this manner in response to a single customer.
Thus, for years at a time, the supply of bandwidth is effectively fixed. With a fixed supply of bandwidth, they can only lease so much. We have agreed that the reservation amount per bandwidth leased is not relevant. The model you want to look at has a vertical supply curve.
Finally, the theory that says consumer price should be the producer's marginal cost is predicated on the assumption that barriers to entry are low. This is not at all the case in ISPs. There is lots of expensive hardware, and there is a significant amount of technical expertise required. Thus, we cannot apply the standard econ 101 model, because we have violated its assumptions.