Mass transit is cheaper than owning a car without subsidies. However there is a large hurdle before the word mass applies. The bus I took to work this morning had a peak of 5 people on it - it was only cheaper because of subsidies. If there were 100 people on it (it only has ~30 seats, and the route doesn't allow a bigger bus - but ignoring reality...) the fare would pay for the bus, driver and be less than everybody having their own car.