That $0.56 number includes depreciation. There are other costs like insurance which are non-trivial. Initially at least, it's not going to be much less.
At any rate, this eventual reduction in insurance is why I started by saying "Initially at least". With time, the cost of manufacturing self driving cars will also go down.
Electric vehicles would depreciate at a much slower rate than ICE vehicles, as the only components that wear would be moving parts (electric motor, fans for cabin comfort) and any degradation to the battery pack (Tesla has packs at 500K miles that still have 80% capacity).