> * Economies of scale. Autonomous cars will likely be of a different design than manual ones so the price of a manual-drive will likely increase- where will the increased money to buy them come from?

I'm not sure how big of a threat that is. The design ought not need to be so different that the same production lines can't easily make both versions. Relative to many newer cars (anything drive-by-wire), autonomy probably only requires the addition of sensors and a computer. Even getting rid of the steering wheel and all driving controls could probably be done modularly on a car model that's offered in both self-driving and traditional options.