The discrepancy is there are ~millions of years of evolution to account for our ability to immediately process and react to unexpected actions around us - whereas self driving cars, doubtlessly, will not be debuted to the public with nearly as much complexity - humans are not designed with affordability and profit in mind. Theoretically, what you're saying is correct, but the practical reality is likely to be a lot different. The best possible implementation isn't likely to be the one which hits the mass market.