What gives you this impression? They have amazing engineers and huge backers. My impression is that they are one of the most likely to succeed in this space.
Lilium responded to the aerokurier article on Monday with an email in which our experts were accused of having set the hover efficiency of the drives far too low with an efficiency of 20 percent. Lilium, on the other hand, claims that values "of 85-95% are the industry standard for turbo fan levels". According to Lilium, this mistake should have been noticed by any industry expert.
Lilium is right with regard to the efficiency of turbofan engines viewed in isolation, as they are standard today on all high and fast flying airliners. However: There are no turbo fans installed on the Lilium Jet. They are jacketed propellers driven by electric motors.
Certainly the history of the automobile should show that such statements can look ridiculous in hindsight.
To move something in the air inherently uses more energy than any sort of ground transport. To make the aircraft more efficient, you have cut weight, which means more exotic (i.e. expensive) materials. The powerplant has to have a higher power:weight ratio (again more expensive). It's more dangerous to be flying, so you need additional safety equipment that ground vehicles don't need. Etc, etc.
And if any aviation technologies manages to gain price/performance better than the stuff used for ground transport... it will be adopted by ground transport. Which still leaves air transport more expensive for the reasons listed above and many others. Hell, in WW2, they stuck an aircraft engine into the most common US tank (sherman). Interestingly, sherman tank crews didn't have to worry about falling out of the sky and dying if their engine failed (though they had lots of other worries, of course).
Long story short: there is nothing magical about electric motors turning propellers. And battery energy density is utterly horrible vs gasoline/kerosene. Air transport will ALWAYS be more expensive than ground transport. Perhaps someday it will be cheap enough to be common. But personally, I doubt that such a day is anytime soon.
Last aside... You can buy a small used two or four seater plane NOW for < $100k. Get a pilots license and you can fly around to your heart's content. General passenger aviation today is not reserved for the ultra rich.
… if the object is heavy. Bats hit 99.5 mph in level flight: https://www.audubon.org/news/the-common-swift-no-longer-fast...
2. This entirely depends on the speed. For high speeds an airplane can be more efficient than ground based transportation. See von Karman efficiency, eg : https://www.researchgate.net/profile/Omer-Kinaci/publication...
3. Exotic materials like aluminum and carbon fiber? The BMW i3 adopted the latter for example
4. A better way to look at it isn’t whether air transport will ever be cheaper, but whether air transport can be cheap enough to be worth it due to the unique advantages it offers. Eg flying in a straight line, flying faster, no traffic, relatively easy autonomy compared to ground, etc