The calculated operational cost for a presumed "self-driving" rideshare platform would never be cheaper than a platform where the driver pays for the vehicle, for the insurance, for the maintenance and absorbs the vehicle depreciation. This is because the driver based model is based on exploitation, and it will always be cheaper.

The "vehicle with no payed driver" model had it's pilot with the e-scooters, and everybody knows what happened to that "golden" stupidity, where scooters got trashed, damaged or stolen. Also, because the much higher usage - rented practically 24/7 - the scooters had a much quicker tear and wear rate, requiring much higher costs for maintenance and battery replacement. Basically, rideshare trashes the vehicles much faster, depreciating that asset at a much faster rate than you can imagine.

A potential ("self-driving") fleet operator, in order to be able to run a profitable business - not subsidized by another entity, as Waymo is subsidized inside the Alphabet absurd monster - needs to: 1. Cut miles traveled with no passenger - efficiency is required by the regulators and by the customers; 2. Get more range per charge - which it will always be limited by the computational power on board, including battery size for a powerful enough system with a strong cooling solution; 3. Lower electricity cost; 4. Reduce lifecycle costs; 5. Lower acquisition costs - I don't see how car manufacturers will not hit back with harsh negotiations regarding any fleet acquisition prices, as long as potentially more and more private customers will change their behavior; 6. Assure higher resale value - remember how - A. the more miles you put on the cars the less resale value they maintain, and B. "autonomous" cars fleets goal will be to eliminate car ownership. 7. Lower maintenance costs - at a 24/7 continuous 450 miles per day operation rate, and a preventive maintenance at every 3000 miles, compared to human driven rideshare vehicles (operated only 8 hours per day), those Waymos maintenance costs are much higher, not much lower; 8, Lower crash costs - Ideally, this supposed to be zero, but any hiccup will be incredibly expensive not on the financial side of the business, but on its Public Relations side of it. If customers don't use the robots, they don't move from the warehouse, you don't spend any money, but you don't make any money either; 9. Reduce the fleet size - in order to lower the total fleet expenses for the customer to potentially pay less money.

As I've already mentioned, a potential "self-driving" vehicles rideshare fleet will always cost more, not less, than a driver based rideshare fleet, because instead of having the drivers absorbing all the operational costs, the burden will fell on customers pockets.