Thanks, I wasn't aware of Car2Go. Their price rates http://www.car2go.com/sandiego/en/affordable-rates/ might give a good idea about how expensive using a driverless car would be if it existed today.

Assuming, that the San Diego prices can be applied to Francisco, it seems like taking such a car from downtown to the airport would be about the same as the BART subway. I assume, that would be too expensive for a daily commute.