This is an R&D cost thing and the right analogy is to the telephone operator. It obviously cost a lot more to build even the first electromechanical last mile exchanges (with Strowager / SXS switches) than to hire some young women to work as operators, let alone to design something like System X (a computerised telephone exchange used in most of the UK from the 1980s) but you don't have to keep paying for the R&D on an ongoing basis. The girls married, or got less boring jobs, or just left work, each time you must recruit and train replacements - but you design System X once and use it for forty years no problem.
There are still System X exchanges in the UK to this day, it works fine, so why not. Eventually as copper last miles are discontinued these exchanges will be virtualised, and in some sense System X is then banished to museums like the Strowager electro-mechanical systems I saw as a child.
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.
There are still System X exchanges in the UK to this day, it works fine, so why not. Eventually as copper last miles are discontinued these exchanges will be virtualised, and in some sense System X is then banished to museums like the Strowager electro-mechanical systems I saw as a child.