It's public transport - does it even need to pay for itself?
Almost free public transportation helps people lead richer lives, so its also a productivity/quality of life issue.
I disagree. that's absolutely not a valid conclusion for a service (public transport, road infrastructure, healthcare, etc) that has a substantial benefit to society as a whole.
i.e. providing it at low or no cost at point of use can be a great idea.
This makes no sense whatsoever. That conclusion does not follow - that's what the above comment says.