Only need to be better than human drivers
They don't need to be foolproof - they only need to be better than human drivers. And they definitely will be - we just don't know whether that's 1 or 10 or 50 years. Massively better.
When (not if) the risk becomes less than a human driver, then insurance will cost less. If It's up to society to make insurance work, and to stop lawyers trying to make money by sue-ing the programmer.