The best solution. No fares. Government provided infrastructure shouldn't be gated by cost. You then are essentially saying poor people can't have access to these things because they don't pay enough taxes and that's literally the opposite of why we have taxes and governments. If the point was to only serve those with money we'd just need businesses. Not also governments.
Imagine all the fare inspectors you don't have to pay, all the fare collection equipment and technology, contracts to software companies to make and integrate a mobile app, credit card processing fees...
It raises an interesting question; if it were feasible to implent without massive privacy concerns, would you support income-proportional fee structure for government services? I'm imagining below a certain cutoff income-bracket, everything would be free.
Well, I would in the terms that taxes are literally that. Our taxes pay for the service, you shouldn't need to pay again to use it. You already paid for it. I wouldn't replace taxes with a proportional fee structure either. This is what living in a society is. Sometimes you'll put money towards something that you'll never use, sometimes you'll use something far more than what you paid for. A government and really, a society, or community is only as inversely strong (weak?) as its most selfish person. I've seen a lot of people recently who are applying logic that they wouldn't give 100 starving people a meal if one of them didn't "deserve" it. We need to fix this mentality or we are doomed as a society and frankly, with that line of thinking, I'd question why government bodies even exist since the people pay most of the taxes.