The thing about public bus systems is that none of them are financially sustainable. If they were, you wouldn't need a government to run them. My local system

The thing about public bus systems is that none of them are financially sustainable. If they were, you wouldn't need a government to run them. My local system collects about 1/3rd of the annual operational costs and none of the (sizable) capital & infrastructural costs in fares. The choice to collect insufficient fares versus collecting no fares at all, has secondary effects - fewer people choose to ride, spending any money is a psychological nudge against taking the trip, especially if you're not sure how much money you're going to have to spend. The car historically appears to be ~free, while the bus demands exact change in an impatient voice. You can solve the change issue with cards, but you could also just not charge fares. Let's say you double ridership by taking away fares. This doubling adds approximately nothing to your considerable costs, but you get twice as much direct social benefit, and the price you pay for it is having to cover ~100% of the program cost using taxes instead of ~90%. On top of this you get secondary social benefit - buses move people so much more efficiently than cars that traffic speeds up dramatically, and you don't need to perform continuous expansion of the road network to accommodate ever-growing traffic problems. The labor value of those hours stuck in traffic alone covers the whole program, even if that value isn't something you can practically "capture" for some kind of profit.