You're making the assumption that there's no maintenance costs involved with non self driving cars. The costs are a bit higher depending on the technology used

You're making the assumption that there's no maintenance costs involved with non self driving cars. The costs are a bit higher depending on the technology used but the cost is spread across 4x paying customers and a car thats able to service customers 24x7 which is about double the productivity of a non self driving car. Technology drives costs down, and once companies figure out best practices on self driving cars, many smaller companies will start copying the approach.