By public accounts, the total hardware costs for one SDC is around $300k. If you amortize that over a 5 year lifespan & 50 rides a day, you get $3.28 of variable costs per ride.
$3.28 variable cost per ride is less than what Uber is paying its drivers (median pay is ~$10.88 per ride). I imagine it nets out significantly in SDC's favor after adding back in cost of gas, insurance, and maintenance. And, the $300k should decrease over time.
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.
$3.28 variable cost per ride is less than what Uber is paying its drivers (median pay is ~$10.88 per ride). I imagine it nets out significantly in SDC's favor after adding back in cost of gas, insurance, and maintenance. And, the $300k should decrease over time.