If the household can make all its trips by public transit, then that’s by far the cheapest option. But suppose it cannot. How many Uber rides can it afford to take before owning a car becomes cheaper?
If Uber costs about $20 per ride — about what an UberX costs now for a 5-mile ride in New York in moderate traffic — then the household can make up to about 15 percent of its trips by Uber and the combination of Uber and public transit will remain cheaper than owning a car. On the one hand, that figure implies that the household still needs excellent access to public transit since it must make 85 percent of its journeys that way. On the other hand, 15 percent of 2,000 trips is still 300 Uber rides per year."
Source: FiveThirtyEight, 28th August 2015