Oh, I wouldn't want to ignore micro-econ1. I must agree with you that it's not going to be a substitute for a family car. But I don't think that rules out some other business model, like community owned vehicles.
It is in the same price range as small aircraft, and I understand that small aircraft were and are fairly common in wilderness regions. Availability would influence a frontier region considerably. So I'm trying to inflate the price and limit the numbers available by positing that even though to planet's TL is 12, the planetary population of 50 million are too few to support a grav module factory.1 Although that wouldn't make it fantasy, it would make it bad SF.
Hans
No need to inflate the price. If the planet is anywhere near a planet that produces the modules already, you probably can count on the macro econ theory of comparative advantage to keep from having any such factory on a world with that small of a pop.