Per non-adjusted output manufacturing employs fewer than Farming, and farming employs fewer people than hunting and gathering. I'm not totally disagreeing with you. I just think this a turtles all the way down situation.

"Reliable cars" have built in positives for the consumers productivity (they're reliable).

Yes, the majority of economists have considered that and it's why they love automation so much! As costs to produce goods come down, competition (in a competitive market) forces the end price down. Then the end consumer saves money! In your example if the costs hit zero while the consumers still have money then it's a complete miracle!

For a capitalist, the best state of affairs is when everyone can consume her products with enough margin to beat other possible places to invest capital! If automation is adopted, it's because it gets a factory closer to that point.