See the first NYT article:
> Every second of every day, the M.T.A. pays $83 in interest. That’s $7.1 million in 24 hours; for the year, a total of $2.603 billion. Those costs consume 16 percent of the transit agency’s budget, nearly three times as much as in 2002, according to the state comptroller, Thomas P. DiNapoli.
https://mobile.nytimes.com/2017/11/16/nyregion/subway-new-yo...
The alternative - to wait until you've accumulated enough cash to build a bus depot - seems kind of a bad idea.
That is what is happening at the MTA.
The car bridges and tunnels into and out of Manhattan are at full capacity all day long. It is vastly faster to take the subway in most normal cases.
That being said, it isn't a public enterprise, and its not immediately clear (to me) what the cost of capital for a government enterprise is.
hah. vanguard's VNYTX (NY long term bonds) has historically done better than inflation, and that's after costs and such.
spot checking MTA bonds available on etrade, i'm not seeing anything nearly as low as inflation. (looks like ~4.5%? not a rigorously computed mean.)