I own a pickup truck, though I don't use it more than once or twice a month. Pretty low usage (and shitty gas mileage) for a vehicle worth $30-40,000. It would be cheaper to just pay to have everything delivered, or rent a truck when I need one. But the convenience of having it outweighs the cost. The same could be said of a sports car, a boat, am RV, or even a light aircraft.
Why is it you think that the cost of use and maintenance really matters? If that were the case we'd all drive small 2 or 4 door sedans and nobody would both with an SUV, which is large, seats barely more than a 4 door sedan, and cost 3-4X as much to both buy and maintain.
Do I care if it costs me $1/mile to fly? Depends...if I can get my parents house in 20 minutes and spend $40, compared to 1.5 hours and spend $15-20 in a car, there's a pretty high chance I'm going to fly. A trip to DC is 300 miles. If there are 2 or more of us going, it's still cheaper than a commercial flight, faster than a commercial flight (door to door), and I go when it fits my schedule.
Not everyone is cash poor. Not everyone has a severely limited budget. It's why I mentioned somewhere in this story that it's likely that just being a a 2%er would be enough to comfortably own a flying car (400k+/year). And yet there are 6 Million 2%ers in the US. There is a market for it, just as there is a market for Teslas and Beach houses and $3000/night rooms on a atoll in the Pacific. Just because you just aren't part of it doesn't mean it doesn't exist.