But I'd argue that concern is backwards. First, go for correctness. Perfect the algorithm and sensors, get the car working. Then look at scaling down the technology and making it cheaper. The fact that Google doesn't make cars (a point the author made) is kind of irrelevant, because this is a sensor/control/software problem, not a car problem.
Recognize that BMW/Daimler/et al really don't want true self driving cars. It's not really in their interest, because it would radically reduce the need for car ownership and would open up a new world of on-the-fly car rental. Human drivers required = good business. I'm not saying its a conspiracy, just that they have no passion to disrupt their industry in this way.
Even the cost is somewhat moot if the business model is different. Let's say the Google Car sensor package costs $100,000. That's cost prohibitive for individual ownership, but it would not be a problem for a business model like ZipCar + Uber, where you call a car on your mobile phone to get you, and 'rent it' for a short self-driving or assisted trip. If car use moves from ownership to renting, then many people can spread the cost of the sensors.