[hedora]

If the car fleet kills half as many people as a human with a $1000/car system, and zero people with a $100,000 system, then we should immediately put the $1000 system on 100 times as many cars as we could put the $100,000 system on. (I picked those numbers because that is the order of magnitude range I have heard self driving car companies quote.)

The $100,000 system would only ever make sense if the fleet was already entirely self driving, and money for other life saving stuff like the environment and health care also hit suitable diminishing returns. Of course, by then, the cheap systems will have improved.

This argument holds for any non-negative dollar value you place on human life.

It is also independent of who owns the vehicles. Money the bus fleet spends in expensive self driving pulls money away from bus stop upgrades, pollution controls, etc, etc.