The opportunity cost is still high. With your own car, you can go wherever you want, when you want, stay as long as you want and come home whenever you want.
With public transportation, you must be flexible and able to plan their trip.
Competition helps some prices under control. When I was a baker by profession, and if I could get $ 5.00 for a loaf of bread, I charge $ 5.00 for bread, even if it costs me to do only $ 0.75. Competition prevents me from doing so. But if I can away with it, you can be sure that other bakers will begin to charge the $ 5.00 for a loaf of bread. Think it can not happen? Look at the airline industry. It requires an airline to start charging for extras. They all followed, when the saw away really the only airline with additional costs and make big money on something that costs almost nothing.
So, insurance companies, workshops, shops and other parts of expenditure as a minimum, it costs them. But you can be sure they are charging so much to think about how they get away with it.
This is called the Free Market or Free Enterprise.