Difficult to put a price on it (I can't afford
any new vehicle right now, let alone one with autonomous features of any level), but I like
Alex Roy's take on what self-driving cars should offer. More augmentation than economy. Humans still in control, but airline-style failsafes that prevent the human from getting into trouble.
Things like ABS and stability control already do it to a degree but he argues they're primitive and misunderstood (how many regular normal drivers actually know what ABS is, what it does, or what it allows them to do in an emergency, despite it being available on vehicles for decades?), but extra augmentation would do things like prevent a driver from accidentally pulling out of a junction into the path of a motorcycle the driver hasn't seen, or not allow a steering response that would pull someone on the freeway into the path of a truck.
I've driven a few cars that fit into the Level 2 definition. Their main benefit, I think, is in reducing the mental processing of certain types of journey. I'm not a fan of semi-autonomous functions really (I don't even like active cruise control - I prefer to just set a speed and cancel it myself), but a few trips in Mercedes with automated steering, accelerating and braking in highway driving suggest it could reduce fatigue.
It's similar to how regular cruise control is quite nice if you're just going to be driving for hours in a straight line on a mostly empty road. It frees up certain physical functions so the important stuff like looking where you're going becomes less tiring. You can afford to relax your limbs a bit, basically, and that does take some of the exertion out of long, boring trips.
The one situation I always kinda wish I was driving something semi-autonomous is when I'm doing my semi-frequent journeys back from airports after some event or other. It's usually in the evening, quite frequently at rush hour, and because this is the UK, it's often either dark, poor weather, or both. People around me are doing stupid things, some people are being dozy, others aggressive, the traffic constantly ebbs and flows, you're squinting through the raindrops and dazzle from headlights and taillights... having the car take at least some of the work out of that high-duty environment does leave you feeling much fresher at the end of the trip, and probably less liable to make a mistake during it.