Infrastructure scales pretty well with density. You run more miles of pipe to cover less dense regions. Power lines pass more people per mile. Same with fiber.

Infrastructure scales pretty well with density. You run more miles of pipe to cover less dense regions. Power lines pass more people per mile. Same with fiber. A single cell tower covers more people. With enough density that walking out biking is possible, you need fewer highways or subways to move the same number of people. Sidewalks are dirt cheap! You might be amazed at how the infrastructure costs aren't very high, and with more people you have more sources of income