A car, as a mode of transportation, is a box that moves. You can buy one for twenty grand. It has a roof, four wheels, doors and an engine. The engine turns the wheels, the car moves, you get where you're going.

If you can get that functionality for twenty grand, a car that costs 100X as much must offer improvements over that functionality.

Is the car 100 times faster? No.
Is it 100 times more fuel efficient? No. Is it 100 times more durable, e.g. will it last for 100 times as long? No. Is it 100 times prettier? Debatable. Some cars are indeed beautiful. A hundred times more beautiful? Doubtful. You would have to go a LONG way in terms of design and materials to objectively state that the car is 100 times "better" than a cheap beater.

So objectively, there's no way to argue a car is 100 times better than another car. What about subjectively then?

Is you car really 'worth' 2.5M? What benefit do you receive from paying 2.5 million dollars for a car, other than SAYING you paid 2.5 million dollars for a car? So why do we stop there? Why aren't there 120 million dollar cars? Or a billion? If we're just pricing things for the sake of being able to say we spent more on our possessions, why stop so low? Because there's a line? Somewhere between 20,000 and a billion is the sweet spot, the amount you 'should' pay for a car? We've already established that there's no objective 'should' that results in a 2.5 million dollar car, so why did we stop there?

I get that paying 2.5 million for a car is an exercise in self-aggrandizement, but is there not something seriously wrong with a society that doesn't stop people from spending obscene amounts of money for nothing more than vanity? (Or more accurately, that allows such disparity that some people CAN spend obscene amounts of money on vanity while others are struggling to feed and house themselves?)