Earlier quoted context omitted.
The MTA is a state agency, so really you need to look at the state's budget, not the city's. I also have little sympathy for the argument that the MTA is too short on cash -- they have been wasting enormous amounts of tax dollars on failed projects for decades. Not that that should give us any hope for an expanded subway system.
Are the state finances in any better shape? The tolls on the new Tappen Zee bridge are expected to be $15, and even that might not be enough to fund it after the hole Coumo blew in the transportation budget after deciding to pillage a general fund instead of raising tolls for commercial vehicles last year.
In my earlier comment I mentioned the Rockaway Beach Branch. That right-of-way would require only a bit of cleanup, some maintenance on a few bridges, and switches to connect to the A line and hundred feet of tunnel in Rego Park, and we would have a new subway line in Queens with access to JFK. We are talking maybe a hundred million dollars, assuming competent engineers and contractors are hired -- a fraction of what the MTA has been spending trying to get the Rail Control Center online.