An SDC has many of the same operational costs (and maybe more) than a human-driven car. (Also garaging, cleaning, etc. As well as the support staff if a car gets in trouble somehow.) You can admittedly assume electric and assume operational costs may be lower than say a Prius today. But I don't consider it a given that a company which purchases and operates an SDC fleet from Waymo can operate profitably while undercutting rideshare as it exists today.
That includes electrical and maintenance. That's still less than a regular car, but it's still a larger number than most people consider.
It would be possible to say its less, though I'd tend to suggest it would be more than the Prius since there's no human custodian of the car to handle the "pull over, I've gotta puke" situations which can add unexpected expenses.
