It costs that much because people are willing to pay more for better sound, better noise cancelling, etc, even if the returns are diminishing. Perhaps a $500 pair of headphones only sounds 3% better than a $200 pair. But people will still shell out for better headphones. Sometimes they just think it is better even if it isn't actually measurably better. The existence of numerous successful products on the market is evidence that this is a niche where people are willing to pay for such products.

It's kinda like, who decided that TVs and phones should cost the same? Or who decided that a khinkali should cost 3 times as much as a xiaolongbao?

My Sony XM3's still going something like 8 years now. Incredible value.

I have a lot of Apple gear, these would be obvious next choice because of integration, but I struggle to justify why otherwise. They heavy, going to pain to repair and cost much more.

How much is your house worth? Whatever someone is willing to pay for it today. That's it. There's no right price. If they can cover costs and make a profit (or better yet a huge profit), then they're pricing it right. Sure, it doesn't work for you. It doesn't work for me either, which is why I don't have a pair. But they seem to be profitable, so there are enough people out there that want them. I just got off a plane a couple days ago and three people within one row around me each had AirPods Max on. Go figure. They're the new status symbol, I guess.

Wait til you find out about literally every other area of discretionary spending.

I mean, if we're talking any pair of headphones... a good Television certainly costs more than that, why should good sound be less worthy if investment?