Well it depends on their competition and what the market will bear. If they have competitors with a similar-quality product that is undercutting them on price, Waymo will have to lower prices to compete.

And regardless, there's always a ceiling when it comes to what people will pay. In the case of a robotaxi there's of course significant marginal cost to expand the fleet of vehicles, but if they can make more money with more cars at a lower price point (than fewer cars at a higher price point), then they'll do so.