I mostly agree.

> You can pick free, or scalable, or financially sustainable (and without sustainability, a political shift will kill it), but you cannot have all three at once.

Real polities are of finite size, so you don't need (infinitely) scalable.

Here in Singapore we could sustainably afford to make public transport free, if we wanted to.

However I agree with you that charging for public transport is the right thing to do. (And to charge users of government provided services in general for everything, and to give poor people money.) If nothing else, you at least want to charge for congestion at peak hours, so that there's always an epsilon of capacity left even at rush hour, so any single person who wants to board the train at prevailing prices can do so.