People are expensive. Very expensive. Covering 24h/day requires 4.7 regular week workers, which in the UK will cost (for workers over 25) a minimum of £80k. That's just raw salary and basic taxes, other things push it up (as well as the fact that you can't get people to work exact hours consistently so well and people are I'll, etc). So per "baseload" taxi, that's likely £100k/year minimum in human costs in the UK. If the tech has only a few year lifespan you've still got north of a quarter of a million to spend on the self driving things alone.

The number of hours per day the car needs cleaning will be drastically lower than the hours it needs driving.