Cost is the least of the worries. The idea itself is a total safety nightmare. Just imagine having lines of helicopters criss-crossing above every house in every city. Just from structural fatigue failures alone, thousands would be falling out of the skies and smashing through roofs every day.
The Jetsons cartoon didn't use powered hovering, the vehicles magically floated. Lighter than air would be required. But then wind would become a huge safety issue. There's just no sensible engineering solution for a flying car.
Maybe could be a flying bus/train solution where the routes and vehicle count are both limited and well managed on a city wide scale. No flying over any houses at all, for example. And a few hundred highly maintained collective vehicles, per city, instead of a few million selfish owners.