Explain how a car with a human driver will be cheaper or have price parity with a car that requires no paid human driver. The driver is the most expensive part of every ride. And that's before tip.
Uber outsourced they capital intensive fleet of cars to the drivers. Waymo has no such luxury.
But the main point is: if there is no need to compete in price, companies won't do it. There is no other company offering driverless rides and even if Google were to have huge margins on every ride, they wouldn't lower prices.
Happens all the time that companies literally just choose to not compete in price because people don't have options or just have accepted a specific price level.
Yeah, manufactured goods aren't exactly known to increase in price as production scales. This is a very temporary anomaly. Cars with drivers are on the precipice of becoming extinct, save for specialty needs and the wealthy.