There are laws relating to the conservation/conversion of energy. The air car idea is about one thing. Defying them. Just like electric cars. They are pie in sky feel good nonsense.
Put a 700ft lb diesel engine in a 6000 pound F350 and you get mileage near 20 mpg. Put a 1000cc engine with 80HP in mostly plastic car and maybe you get 40-50 with a tailwind.
The micro car struggles to climb hills or accelerate. It cannot transport enough groceries to feed a family of 4 for a week so you make multiple trips. It cannot accelerate quickly and as you have to floor it to get any performance, components are stressed and wear faster thus requiring more frequent replacement.
It requires many composite materials and other lightweight tricks all of which cost more and require more energy to produce than steel and diesel.
the entire econobox has a limited lifespan and hits the scrapper far quicker, again consuming energy for it’s recycling.
In the mean time, the big Ford is good for 300,000 miles, does not struggle in traffic, can make fewer trips because of greater carrying capacity, uses more easily obtained materials such as steel and diesel and is easily recycled in the big picture by comparison.
Over the lifetime of the two, the econobox takes more energy.
I know someone who built a lead-acid truck that can go 80 MPH, climb hills no problem, and has a range of 100+ miles, all using low-tech components (no regenerative, etc). It would be even better if he could swing the cost of an induction motor and controller. The benefits, he stated, were that the batteries are housed in the bed of the truck which is designed to carry weight, it’s completely separate from the cab and enclosed in case of accident, and we’ve been recycling lead-acid batteries for 100 years with virtually no waste of the working materials (copper, lead). Lead’s health effects are well-known and techniques to work with it safely have been in place for decades. This is much in the vein of your post - that the total cost is more important than the “feel good” aspects of this. And, lead-acid batteries, until the regulations and artificial shortages of lead hit, are inherently cheap to build and buy.