No form of transportation "pays for itself." No transportation system ever devised is some sort of profit-generating vehicle, nor is it meant to be. It is merely a means of transportation and the ability to distribute work more efficiently.
I love how the anti-rail, pro-auto movement has somehow through slight-of-hand methods convinced everyone that freeways and airlines are somehow profitable businesses or infrastructure. Airlines would not exist without massive subsidies from the government on various levels(direct subsidies, bailouts, cheap fuel, airports, ect.) just as roadways are built and maintained with billions of dollars of public money, and are used by cars, which are major investments on the part of the individual for the car itself, fuel, repair. Lastly also ignored is the cost of the infrastructure required to generate and protect the fuel supplies in order to drive or fly around. These systems both consume well over a trillion dollars in added up costs every year to operate.
I'm quite tired of light rail being posed as some sort of massive public expense with no benefits, when the real costs of the auto and air-based travel systems are hidden and are somehow projected as free, no-cost/all-benefit methods of transportation. Air and road travel are respectively the most expensive methods of transport when all costs are considered. A multi-tiered flexible transportation network with many diverse layers should be and is offered by all major cities with any hope of a future in a globalized economy to move people and goods. If done right on well-developed networks(which barely exist in the US other than the Northeast), rail is the cheapest form of transportation of people and goods on land. Only travelling by boat is more efficient.