Don't get too used to paying $104 for your 30-day unlimited MetroCard. The MTA is already aiming to raise fares again in 2013 (possibly dwarfing the last hike) and Streetsblog points out that a report from the State's Comptrollers office [PDF] paints a scary picture in which things could get much worse.

The gist of the problem is that the MTA's 2010-2014 capital plan—which covers both system expansion and maintenance—"has a $9.9 billion funding shortfall, and only the first two years are fully funded." The current plan assumes that the state and localities will fill the gap, but you know what they say about assuming. If the state doesn't help out, we'll be back in a position where the MTA will have to either cut more services, raise fares, take on more debt (which is part of the agency's problem already), or some combination of the above.

And, for instance, if the MTA were to choose to borrow the nearly $10 billion needed to fill the gap, its current debt services would nearly double in ten years, "growing from $1.9 billion in 2010 to $3.6 billion in 2019." According to the Comptrollers office, "Such a heavy reliance on debt would place a serious burden on the operating budget, just as heavy borrowing in the past has contributed to the MTA’s current fiscal crisis."

To pay off that additional debt "according to Neysa Pranger of the Regional Plan Association, the MTA would need between $1 billion and $1.5 billion in new annual revenues." And you know where that would come from? We'll give you a hint—it wouldn't be ad-wrapped subway cars or taxing MetroCard artists.

Streetsblog does some back of the envelope calculations and concludes that if the MTA were to take on that debt and then use fare hikes to pay for the extra costs (and were to distribute the hike evenly across different types of fares) we could be seeing "a base fare between $2.80 and $3.00 and a monthly pass between $129 and $137.50 by 2014."