There is no such thing as overusing a thing that is sold as unlimited. It's true that the train company does some probability math and figures out some balance

There is no such thing as overusing a thing that is sold as unlimited. It's true that the train company does some probability math and figures out some balance point for the proper price for the ticket based on some estimated bell curve of usage, just like a diner selling a "bottomless" cup of coffee for $1. But that doesn't make the right half of the curve "overusing" any more than it makes the left half of the curve "underusing". They are all merely using the thing that the supplier sold in accordance with the terms set by the supplier.