Purchase price

Airplanes are times more complex than cars.

The price of an aircraft is not bound solely to its design. Even though not luxurious as an A380, general aviation planes are still expensive because they must also be reliable. You can't just build an aircraft and start selling it. It must be certified by international organizations, such as EASA and FAA, and that is not cheap.

Before a newly developed aircraft model may enter into operation, it must obtain a type certificate from the responsible aviation regulatory authority. Since 2003, EASA is responsible for the certification of aircraft in the EU and for some European non-EU Countries. This certificate testifies that the type of aircraft meets the safety requirements set by the European Union. (source)

Not only that costs money, but also time. On average, a new GA aircraft will take 3 years to be certified (Fonte).

Not just the certification organizations fees that are high, but to test requires multiple prototypes. And if the plane fails any safety assertions, then it goes back to design phase. Every single component, from the flaps to the belts, must be tested under all kinds of conditions.

The demand also counts. Unlike cars, most people don't buy planes because they don't have to. And even if they buy, they don't usually change their planes every year. For example, Cirrus SR22 was first produced on 2001 and until 2016 only ~5000 units were sold (Fonte). It took 15 years to sell 5000 units. That makes this aircraft to cost 629,900 USD (2019).

But still, you can find a Cessna 172 for the price of a 2019 Lamborghini Urus (200,000 USD).

Custo operacional

Ok, so you signed the deal and bought your Cessna 172. Now you have to deal with maintenance, fuel, oil, landing fees, hangar rental and all. And of course, insurance!

1. Maintenance (fuel, oil, landing fees): 17,850 USD (300 hours)
2. Insurance: 5,000 - 10,000 USD
3. Hangar: 1,800 - 12,000 USD / year

(source)

It's estimated to cost you 29,650 USD per year to maintain your new Cessna 172.

Simple: short production numbers. If light airplanes were as common as motor cars, manufactured by the millions, they would be much cheaper...

New planes? They are indeed luxurious, with panels that make a modern car look simple. Have you seen the multipanel displays that are going in? The instrument panel alone is worth more than a new car. A car can be assembled on an assembly line in about a day, yes? With components all trucked in from here & there feeding an assembly line. Planes don't sell in that kind of quantity.

Look at the data here: http://www.fi-aeroweb.com/General-Aviation.html

As of 2019, there are more than 446,000 general aviation aircraft in the worldwide fleet, ranging from small training aircraft and helicopters to intercontinental business jets. About 213,000 of these, or 48%, are based in the United States. There are more than 5,000 public airports in the U.S. vs. fewer than 400 airports served by commercial airlines.

2019 Worldwide plane deliveries: 2,443.

Can manufacuturers dwarf that number.

Toyota’s motor vehicle production reached almost nine million units in the fiscal year ended March 31, 2019. https://www.statista.com/statistics/267272/worldwide-vehicle-production-of-toyota/

And that's just 1 manufacturer. VW, GM, Ford, they're all huge.

Another factor: Just about anyone can get a drivers license and drive a car, with many multi-car households. It takes a fair bit of dedication to get a pilots license, months of training, and then ongoing practice and a minimum of bi-annual recurrency testing/training to keep that license, along with keeping somewhat medically fit. And then supplies like charts that are updated every 6 months, down to 2 weeks for approach plates. When's the last time you updated a car map? I only use the GPS moving map in my car.

Older planes can be retrofitted with the latest and greatest avionics, with equipment costing more than a new car (example, a new Avidyne IFD550 GPS/NAV/COM can be over $15K USD - plus installation).

http://www.nexairstore.com/new-avionics/gps-nav-com/

An engine flown for 100 hours a year can last 20 years, and then it can be overhauled, or replaced for $50K or more.

http://www.airpowerinc.com/productcart/pc/engines.asp?searchParm=ALL&catID=33

Planes get inspected annually, and much more thoroughly than the inspection a state may impose on car owners for 39 a year. Some states there is no inspection at all.

Aluminum planes can be repainted, a thorough process where by everything that can be removed is, and all the bits cleaned & repainted individually, then reassembled. A paint job can cost the same as buying a small car. Repainting a car by comparison is dirt cheap and is done in a few days, https://www.maaco.com/services/auto-painting/

Vs 6-8 weeks for an airplane for disassembly, prep for stripping, cleanup where stripping missing, alodyne to treat the aluminim, primer, finally paint, and then reassembly. Composite planes, I don't know the process.

Operating: planes use a lot more fuel per hour to cover ground a lot faster. Say you had a 180 HP plane burning 10 gal/hr and going 125 mph ground speed (into some headwind). To go 300 miles will take about 2.4 hours, 24 gallons of gas at roughly 5/gallon = 120. A car might average 60 miles/hr, taking 5 hours, and getting 30 mpg, so 300 miles = 10 gallons @ 3/gallon, so 30 in gas.

That 300 mile road distance is almost always fewer air miles. Example, it is 183 nautical miles (210 statute miles) to fly from my home airport to Bangor, Maine, a trip I am making in the next month or two.

1 hour, 26 minute flight. ~15 gallons of fuel $75. (www.skyvector.com)

Driving, 245 miles. 3 hour, 44 minute flight. $25 in fuel plus tolls. (maps.google.com) Longer if there are construction delays (and it is summer construction season where I am) or traffic delays from accidents.

The time savings: 2 hours and 18 minutes. What's your time worth? $50/hr? So $115 saved by flying. Makes up for the difference in fuel cost.

Am I taking my 1973 plane with new paint job and avionics? Or my 2016 car with moving map? The plane for sure.