It costs a lot because the ingredients are expensive and there's a ton of labor involved. Seriously you should see the level of chemistry, preparation, and precision that go into some dishes.
If you can't appreciate it, that's fine. Not everybody gets any given work of art and some people don't get culinary arts at all. But this "fine dining is a scam" thing I've seen in this thread and elsewhere is a bad take. It amounts to "things I don't have the capacity to appreciate are garbage because I lack the ability to understand that others experience the world differently than I do."
Does it get treated as a status symbol? Sure. But all art gets the same treatment. Picasso is no less valid because some rich asshole buys his work.
That said, there's a kernel of truth to the sentiment, but these little mom and pop local places aren't good just because they're cheap. It's that their main competitor at the price point, chain restaurants, are trashy, factory made garbage. There's a lot of mid range chains (or higher end chains, like Ruth's Chris). They make their money by leveraging economies of scale and a consistent product, but there's not any soul to that food. You can usually do better at home for less. Not to denigrate it too much; I've got chain food I like (don't we all enjoy some junk food from time to time?). Hell, I know a Michelin Star chef that has a hot wing at one of the national wing chains he craves, but then that dude eats everything.
Local mom and pops are often immigrants from other nations making food the way they know how ... which often involves more down to earth ingredients and methods instead of processed trash bought from Sysco. I've had some amazing food on the cheap from immigrants from different areas of Mexico, Ethiopia, Czechoslovakia, lots of South East Asian countries ... you name it. They're not all great, but there's been some incredible flavor : value ratios.
So try your local places, but understand that fine dining needn't be a scam if it's a chef busting his ass to be creative and delicious, even if it's very expensive.
I will give credit where credit is due. The best steak I have ever had was some cold leftovers from a very fancy restaurant my parents had visited for an anniversary. I dream of cuts like that again.