The MTA document on service reductions includes the ridership and average cost per ride for every NYC bus route. Even when I was inside NYC Transit, I never saw a tabulation of costs, although ridership was tabulated.
Cost data is provided for LI Bus and MTA Bus Company lines as well, in other reports. And as for rail, it isn’t provided but could be if the MTA would use Metrocard data how much times trains spend on each part of the line to do an estimate as well. Perhaps the cost of maintaining the express tracks could be assigned to outer lines. And for real sophistication, distinguish marginal from average costs, with the marginal cost of additional rush hour riders on the Lexington Avenue line equal to — the cost of the Second Avenue Subway. Finally, look at the dedicated MTA taxes paid by those in different areas, relative to the level of subsidy, not including the portion that is sucked away by the past (debts, unfunded past pensions, etc). The more the better.