There are those who would buy a "roadable" simply for the pleasure of owning such an unusual vehicle, and for them, the price will not be a major consideration. It is to be expected, however, that the size of this market will not be particularly large.
After that, the potential purchaser will consider his options. Would he be better off to simply buy a car, and buy an airplane, and put up with the expense and inconvenience of finding some kind of local transportation when he gets to his destination? Whether a prospective purchaser buys a "modular" or an "integrated" design, the family still has to travel to the airport to change into flight mode. Perhaps they might just as well transfer the baggage, and climb into a regular airplane.
This factor sets the parameters for the pricing of a new dual-purpose vehicle. It should be a figure comparable to the cost of a new car plus the cost of a new airplane. To be really competetive it should be significantly less. For any individual purchaser, the size of the proposed car, and the size of the proposed airplane introduces a host of variables into the mix. However, the bulk of the dual-purpose market will probably be for vehicles that carry a family of four people.
Pricing now becomes a real challenge. For the development of a new automobile alone, it is not uncommon for an automaker to spend millions of dollars. These costs must be amortized over the production run that follows. The development costs of the airplane must be added to that.
None the less, to be truly competitive, any dual-purpose machine must be saleable at a price less than the combined cost of a comparable aircraft and a comparable automobile.