There's more to "capital" than a physical machine.
Compare the cost of creating software (often many millions) to the per unit cost of copies of that software (zero).
Compare the cost of developing a new processor architecture and setting up the manufacturing plant (billions and billions) compared with the per-unit cost.
Compare the cost of building out a physical network infrastructure to cover a city (many millions) compared with the cost of connecting a single user to the box down the street.
Compare the cost to create all of Facebook's hardware and software infrastructure to the marginal cost of adding one more user to the platform.
Compare the cost of creating software (often many millions) to the per unit cost of copies of that software (zero).
Compare the cost of developing a new processor architecture and setting up the manufacturing plant (billions and billions) compared with the per-unit cost.
Compare the cost of building out a physical network infrastructure to cover a city (many millions) compared with the cost of connecting a single user to the box down the street.
Compare the cost to create all of Facebook's hardware and software infrastructure to the marginal cost of adding one more user to the platform.