Wouldn't that requirement completely kill any chance of a L5 system being profitable? If company X is making tons of self-driving cars, and now has to pay insurance for every single one, that's a mountain of cash. They'd go broke immediately.

I realize it would suck to be blamed for something the car did when you weren't driving it, but I'm not sure how else it could be financially feasible.

No? Insurance costs would be passed through to consumers in the form of up-front purchase price. And probably the cost to insure L5 systems for liability will be very low. If it isn't low, the autonomous system isn't very safe.

The way it works in states like California currently is that the permit holder has to post an insurance bond that accidents and judgements are taken out against. It's a fixed overhead.