That’s over and above a) the rest of their transport budget and b) the massive federal subsidy for the D-Ticket.
To look at a UK context Al (sorry) suggests that Uk government spends around £430-£450 on transport per person per year (based on £28 - £30 billion spend on a population of 68 million people), so a similar amount (£40-£45) perhaps wouldn't be too bad in that context.
Also, given that this would primarily benefit residents outside of London, it would also help to alleviate the disparity of spending on transport per person between London and elsewhere.