> assuming the same rate of accidents, but most accidents with a self driving car are the manual driver's fault
This is a very shaky assumption in my view; more realistic would be (to me):
1) Overall accident rate reduction even for manual drivers
2) Reduced damage in accidents even for manual drivers
3) Slight increase in "at-fault" allocation toward manual drivers
It seems very likely to me that those would result in net favorable effects even for manual drivers.
I believe a lot of driving will move to full auto once viable, but not all of it because lots of people like to drive recreationally, and I simply don't see insurance rates for manual drivers spiking out of control-- just compare insurance pricing for less-safe vintage cars, which is also perfectly reasonable.