> As I understand it the marginal cost of the first N gigabytes is approximately zilch, but N+1 gigabytes is $$$$- because they now have to upgrade the infrastr

> As I understand it the marginal cost of the first N gigabytes is approximately zilch, but N+1 gigabytes is $$$$- because they now have to upgrade the infrastructure. Missed out a step there. It's not zero then suddenly $$$$. It's more a question of gradual, usually low cost, equipment upgrades. All backhaul is via fiber optics, so by switching optics you go from 1G/10G/100G to multiple 1G/10G/100G waves. You might need a new router blade or a bigger chassis at some point. Only if you really messed up do you need infrastructure upgrades. This might mean splitting nodes, i.e. pulling a bit more fiber to hotspots, but that is why you have spare empty conduits and excess fiber strands in your cables. If you don't then you truly deserve all the misery you brought upon yourself.