I haven't read of a public transit system where the fares covered the costs of building and operating it. I have read that MTA (NYC), BART(SF), Amtrak, NJTransit, and other US ones definitely are in the red year after year.

It's probably super difficult to exactly quantify how much something costs, but I think it should be provable that public transit is cheaper per person than the maintaining the network of roads we have. Of course, it's also hard to quantify the worth of those roads when we have a natural disaster and public transit stops working...