[sagarm]

Tracks form a network that can be used to reach more than just the directly connected cities.

Similarly, airports require a high up front capital cost and form a network that allows you to reach further than the infrastructure at the starting point allows.

On rail having high maintenance cost for the infrastructure: every flight requires expensive and fragile planes + lots of fuel, so the marginal cost of each trip is high.

So it's a little more complicated to compare the costs than you suggest.