First of all, you need to own and insure a fleet of rolling depreciating assets. Maybe not as much these days with the crazy used car prices, but still, you have put these cars on the books. You can't even really lease the vehicles because of all of the LIDAR and other self driving modifications that are required.
Next you have to keep these vehicles fueled - either gasoline or electricity, so you are going to need to pay people to handle that. And you have ongoing maintenance for brakes, fluids, etc. And space to park them overnight and in low demand times.
And you also have the interior maintenance. Someone has to clean up the puke and garbage and just general messiness of having humans in the backseat of this car. Throughout the day, every day.
And this has to be repeated in every single city while competing against Uber and Lyft and traditional taxi companies that already know that the driver is probably the least expensive part of this whole system.