Only if it's in use 24/7. That won't happen because it'll need charging for a few hours each day. ... At least with a regular taxi, it can be on the road 24/7 with a rota of drivers, so the vehicle "cost per mile driven" is far less as it's used far more.
I don't understand what differences you are assuming between a regular taxi and driverless one. Why would one be electric and not the other, if electric is the best engine option?
Let's imagine that there is a transition vehicle, which still has controls and a drivers seat, so it can be driven by a driver. But it also has the computers and sensors so it can act as a taxi with no driver in the car. So it's exactly the same car, regardless of whether it is being used as a "regular taxi" or a driverless one. Now tell me why it would be more expensive to not have a driver sitting in it?
Then you have all the down time, because it's impossible for it to have full use. If it's stationed in a village, it may only get a few journeys per day. To get better usage, it'll have to be "on call" to go to other villages, then you'd be complaining that it takes too long for it to arrive when it's already in use elsewhere, so you'd expect more than one for your village
whoa! Stop right there! One per village!? If the village currently has 100 private cars parked near its houses, I would expect virtually all of them to vanish, to be replaced by up to 100 driverless taxis. Presumably fewer than 100, because there's probably never a time that all 100 cars need to be in use at the same time, so some of the cost savings will come from reducing that number.
I think you imagining a completely different future to me. The driverless taxi makes the private car obsolete, I'm imagining a world in which 99% of households do not own a private car, because doing so is considerable more expensive than using taxis for every single journey.
The driverless taxi is not mainly a replacement for the "regular taxi", it's a replacement for the privately owned motor car. The elimination of "regular taxis" is just a minor side-effect.