Being run entirely from fares means you are not at the whim of politicians for subsidies and grants that can change overnight with an election, which makes it very hard to think longer term.
I think this is what NYC should be aiming for - operationally covering its own operational costs from fares, advertising and property revenues with then state/federal grants for larger capital projects.
A fee increase to that level in other cities might have the opposite effect of reducing ridership and total revenues, against a largely fixed expense base, condemning the subway to a real "death subway".
The externalities of transport are massive, if a small number of people device to spend 15 minutes more in traffic to save the 8 pounds subway fare, the costs to society are simply astronomical because now everybody else has to spend those 15 minutes more too to get to where they need to go, even if they don't have the option of public transport for their route.
Unlike roads which are entirely funded by government. So a comparison is always going to make "public transport" (ironic considering it's the transport not receiving public funds) look more expensive.
My point really is that "even" £8 isn't that expensive in the grand scheme of things. And that money going into the system allows it to work well.
It's also worth noting buses are much cheaper than the tube and quite accessible compared to a lot of places, though much slower.
I guess they should just buy a car instead, right? Or live in Manhattan and walk to work?
There are much better ways to do this, eg offer discounted trip cards to people on certain social security programs (Medicaid eligibility comes to mind). Price differentiation 101. This should be funded out of social security budgets, not transport budgets IMO.