Is it really that expensive? I know some people who had run a small startup automaker that raised 30-something million. They were about 3 months out from first commercial deliveries (having made a couple dozen prototypes to various degrees, ranging from empty shells to full builds), with about $10m still left in the bank - when the board decided to bring on a guy from Detroit (Paul Wilbur, the guy responsible for the Chevy SSR, and a bunch of other train-wrecks-in-car-form), who then proceeded to run the company into the ground.
Are aircraft that much more expensive than cars, that you can't even build a demonstrator for that kind of money? To be fair, the automaker's vehicle was technically classified as a motorcycle, so their regulations weren't as onerous as for most cars (but they still did full crash and crush tests anyway, voluntarily). But, I mean, they just churned out prototypes one after the next.