Alphabet/Google/Waymo is a technology business, with emphasis on business. They're not running a charity. They're in it to make money. If it's a $20 Uber ride to somewhere, they're not going to leave money on the table and charge $10 because they don't have a driver to pay. They're going to charge $22 for the premium experience because they know people will pay that.
That sounds right. Passenger pays for lower risk, etc. The market sees the company making $2 extra and a competitor will see if they can do it for just $1 extra.
(nobody would confuse me with an economist!)
Of course, but I never claimed that they would do that. At some point though other autonomous services will enter the market and Waymo will have to compete with them on price. Even if that doesn't happen (which seems incredibly unlikely), they're still competing against public transit and people driving themselves (or privately owned self driving cars). Not having to pay a driver means the floor where they can make a profit is lower.
If we're in a world where human driven Uber's are $30, you're right that Waymo probably won't charge $20 just to be nice, even if it only costs them $10. They might charge $20 though if their data shows that it would 10x the number of riders or if they're also competing with another autonomous taxi company.