Not sure where you get that from. Most systems operate at a major loss and are propped up by grants/government funding. Typical targets for operating are ~1/3 of costs are covered by rider fares with the rest coming from grants or government funding.

Since the thread talks about NYC, I pulled this - MTA Budget. In it they state:

In a normal year, farebox revenue constitutes approximately 40 percent of the MTA’s annual budget, or $6.5 billion