rule

The hard truth of it is, the vast majority of people are in reality cloth-eared gits. This is regardless of their level of personal interest in audio quality. Yes, this statement certainly also includes you, whoever is reading it. Your ears and brain are the bottleneck here. Sorry, you actually objectively suck at this. It's biology; too bad you weren't born a rabbit or a dog.

Double blind studies have proven again and again that the products hawked by unscrupulous vendors to audiophiles make no discernible difference whatsoever to listeners, and even a superficial level of knowledge in the laws of physics and/or reality illustrates that the claims they make are usually also impossible.

Further, it is trivially easy to observe that the vast majority of people, possibly everyone, can be fooled into believing that an audio system sounds "better" than before by, without the listener's knowledge, making no changes to the system whatsoever between listening test A and B other than to turn the volume dial up one notch.

Try it on your audiophile friends. Just turn up the volume, fiddle around behind the stack, and claim you installed some expensive crystal or other geegaw. Reveal to them what you actually did only after they've already made up a dozen wine-snob style descriptors about how they thought the "soundstage" or the "brightness" or the "jitter" or whatever the hell was changed. It's a laugh and a half every time.

While this is all very true I would say that it's not all complete nonsense. A decent pair of speakers will still be an upgrade from your televisions built in audio. And some decent headphones will still sound nicer than something at the dollar store.

But you really don't need to spend a lot before you run straight into diminishing returns. A lot of it is also just plain subjective - some people like to hear more bass, some want more clarity. I never went full audiophile but I've tried enough to know that I personally can't tell the difference between a $100 and $200 pair of headphones, so I'm just gonna get the cheaper ones.

edit: Also avoid that cup attachment design in the bottom picture, whoever decided it was a good idea to attach the cups to the headband by a tiny thin plastic nib that's going to break in a strong breeze can suck eggs. Beyerdynamic do it a lot and I hate them for it.
Soundstage is a very real, easily verified things that can be heard in a headphone. A regular cone driver versus planar magnetics will show how wildly different soundstage can be. It's hard to be specific because I'm not an audiophile and don't claim to be one but I did get a pair of planar magnetic headphones from a sale long ago and it changed my entire appreciation for listening.

Music that's played in a studio sounds way different from music played on a laptop. You can hear where in the room the instruments are in relation to one another. A laptop puts all the sounds on the same level, there is no depth to the tones and it sounds flat, as it everyone is sitting on the edge of the stage and playing at the same distance from the same spot. It's artificial and makes some genres hard to listen to because there is so much variation between artists and songs. Studio songs feel more expensive and big.

Headphones that cost more than 300 are not adding anything appreciable but the jump from 50 to 150 is enormous.
- I should clarify that I'm not saying there's no such thing as a distinction between good and crap audio gear.
  
  But it bears repeating, perpetually, that once the threshold of 100% aural reproduction accuracy in regards to the limitations of human hearing is reached, there is nothing to be gained from further throwing money at it. In this field good enough is, in fact, good enough. This is why audiophile scammers have to resort to making up imaginary problems to allegedly cure, using silly inapplicable words like "quantum," or "non-Hertzian frequencies," or whatever. A pair of hypothetical headphones that output totally separated audio, one channel to each ear, reproduced with full range output between 20 and 20,000 Hz without gaps and a flat EQ is literally, mathematically, provably, physically perfect.
  
  We're much better at deluding ourselves into thinking we've gotten some kind of nebulous positive result proportional to the amount we've spent, attempting to justify it to ourselves, than we are at detecting actual differences in audio reproduction. And, what different people think sounds "better" is indeed subjective -- famously so. One listener might prefer a set of speakers or headphones or amp that sounds one way or another, more bass, more treble, whatever. But the fact of it is that once you have removed any imperfections between the production of the original sound and its playback reaching your ear, what you're doing to those tune preferences is in fact deliberately adding purposefully tuned imperfections, which is exactly the kind of thing that audiophiles insist they're trying to abolish. (And to be fair, the notion of a "perfect" audio recording is probably pretty close to unachievable in reality.)
  
  As long as you accept that's what's happening, that's fine. Otherwise, I wouldn't have a big-assed subwoofer in my car.
My standard is to test with very specific songs that have hard to hear nuances in them. If I can't hear those, the gear sucks. If I can, I'm happy. Don't care about anything else sound wise, and I have been able to ball on a budget while still maintaining that standard.

As you said, it's my ears that are the bottleneck, so I go with what works in that regard. There are shitty headphones that can't let me hear what I'm capable of hearing though.
I recently upgraded from sony xm2 headphones to Sennheiser Momentum 4s (and on the way tested Momentum 4 and Bose QC45 side by side). There was tangible difference between the three, and Sennheiser was clearly way better than the two. Having said that, I have bad tinnitus, so any audiophile headphones are wasted one me. But even with the tinnitus, the Momentum 4 is a pleasure to listen to in short bursts

Truth

I feel the cans on the top slide should be ATH-M50 even if they aren't $50. 🤭

“Audiophiles don't use their equipment to listen to your music. Audiophiles use your music to listen to their equipment.” - Alan Parsons

I am not an audiophile, but these things have changed my life. Only $140.

https://www.amazon.com/PHILIPS-X2HR-Professional-Headphones-Detachable/dp/B01N5VHLUG/

I bought this refurbished for $89, and it's awesome! Most comfortable headphones I've used.
- Yeah, I can wear them for hours, and they sound like the band is in the room with you.
is there a dac you recommend in the similar sweet spot of 'you could spend a lot more but you probably won't hear it' ?

best headphone fit I've ever tried. never getting a different set. only wish the bt versions were a little more sleek