The difference between $30 and $300 headphones is significant, but the difference between $300 and $3000 headphones is likely pretty small.

Yes and No. There are so many preferred sounds out there that a $300 and a $3000 headphone are likely to be quite different, and you would expect the $3000 headphone to be technically better, but it comes down to preference. I have a $1000 pair of headphones, and they do just about everything really well, but I also have cheaper headphones that are more accurate (to different target curves, but that is getting into psychoacoustics), or more enjoyable for certain genres.

Price doesn't necessarily correspond to audio quality very well. For example, Ultrasone sells some objectively terrible headphones for $3000.

Probably, I haven't tried those myself tho.

An audiophile would spend more than $25k on a pre-amp, amp, and two speakers. A single speaker cable might cost more than $1000. $300 headphones are vastly better than $30 pair. That is a difference an untrained ear can hear. However they don’t even scratch the surface of high-headphones much less something an audiophile would purchase. A pro level reference headphone might be in the range of 2 or 3k. Pros can hear the difference and properly identify characteristics. A 10k or 15k headphone? Many would conclude that the unbelievable pricing of some ultra expensive audio is snake oil because claims are subjective/unsubstantiated and the science behind them are flimsy or nonexistent.

You forgot the ones who get their direct electricity feed to get pure sine wave.

https://www.youtube.com/watch?v=XJJy6VJvSCk

My hearing is somewhat damaged from years of driving with the windows down. I can't hear any difference, so why bother paying for it.

So because there is a real difference between two pieces of equipment, you no longer think that often audiophiles deceive themselves about differences among other pieces of equipment? I don’t understand the reasoning.