Wouldn’t get your hopes up on it being 90% cheaper—typically Waymo cost the same or slightly more than Uber for me. Obviously the economics change as time goes on but I doubt they will make it that much cheaper.
Without the need of a driver, cars will increasingly be offered as a rental service rather than an ownership object. In a good month, the only expenses I pay for my car is gas, which is 150-200 USD. Do you think driverless car services will somehow be immune to the pressures every other rentier model (actual rent, SaaS, Netflix, etc etc etc) succumbs to?