I feel like a significant percentage of discovery thread posts are essentially variations on the question -
can I get champagne performance on a beer budget?
I see it this way - if you're desperate for Porsche 911 performance but can only afford an MX-5, then my advice is just buy the MX-5 and be happy because they're awesome cars that will give you a very large slice of the 911 experience, and they're terrific value.
Unfortunately some people will buy an MX-5 then claim they're every bit as good as a 911 and that people who purchase 911s are idiots wasting their money. They do this largely to reinforce their purchasing decision, alleviate any residual guilt, and make themselves feel better about not buying a 911 which may be the car they
really want but can't afford. It's this sort of behaviour that's contributed to a lot of the IEM hype bubbles we've seen over the years.
The difference between cars and earphones is audio is very subjective & there's so much variation in the way people hear things that it's easy for the waters to get muddied when it's so difficult to quantify sound quality to begin with. Some people attempt to counter that by clinging to measurements as a form of objective truth, but they're merely one data point that doesn't convey the full story.
So if someone claims "this new $100 IEM sounds as good as that $2000 flagship I heard the other day!" they may be telling the truth, but there's often more to it - that $2000 flagship may be a bass-light reference tuned IEM with great resolution, but the $100 earphone has harder-hitting bass with a more prominent midrange that suits the hip-hop and R&B genres the person listens to much better, so naturally they prefer it.
Most earphone manufacturers use off-the-shelf drivers from Sonion, Knowles or Bellsing, along with DDs that I assume are produced in a relatively small number of factories for a large number of brands. However tolerances & driver matching are generally going to be much stricter on higher priced IEMs, they may use drivers made to their exact specifications or even in some cases DDs or BCDs they've designed themselves, and of course IEM driver counts tend to go up with higher-priced IEMs. The shells themselves are more carefully designed on higher-end models and they'll often have more sound tubes, and crossover components that are more carefully chosen.
How much of that actually translates into audible improvements is completely subjective. You can't measure earphone performance with lap times or 0-100 numbers.
I honestly believe for the overwhelming majority of hobbyists (let alone those outside the hobby) the differences in audio performance between IEMs in the several hundred dollar range to those worth thousands is probably
not worth the massive price jump. Especially once you pass USD $500 or so, diminishing returns start kicking in pretty hard and the improvements become more & more incremental. It's actually amazing the quality of sound you can get for very little money these days.
IEMs
do keep on improving as you get into higher & higher stratospheres however - even my USD $1799 Noble Spartacus are trounced in a number of areas by more expensive IEMs out there! That's what you tend to notice as you climb the ladder, that IEMs don't necessarily improve across the board in every single performance department as you might expect, but rather their potential to deliver in any single area can scale up much higher. So for instance the USD $3k Elysian Annihilator has the highest quality treble and possibly the widest soundstage I've heard, but I'm not a huge fan of its' bass performance - you can probably find an IEM under USD $500 with higher quality bass output, so does that make the Annihilator overpriced? If you're someone who prioritises bass it might.
I'd love to discover an IEM under $200 that delivers performance on par with my USD $1599 UM Mest MKIII, I seriously would. I'm also pretty sure that if UM could build them for that price they'd do so because then they'd move a LOT more units and make much more money. Of course there's always the dream that some unknown brand out there stumbles on a magic formula and bingo, high-end IEMs for entry-level prices - I've no doubt it's the thrill of hunting down the white whale that motivates many people to keep on purchasing budget IEMs, the danger is after awhile when you add up what you've spent you could've bought an actual high-end IEM instead.
So ultimately the answer is no, if you want ultimate performance I'm afraid you do need to pay through the nose to get it - why else would we spend the amounts we do on high-end IEMs if we didn't have to? It isn't for bragging rights, as a music lover I mostly care about making music sound as good as it possibly can for as little as I can get away with spending, but having heard the high end stuff it then becomes more difficult to settle for entry-level or even mid-range gear you know is inferior.
However there's countless brands, virtually an entire industry with compelling financial incentives to convince you that yes you CAN have the ultimate in performance for next to nothing, that this is the next revolutionary level sound you've always dreamed of, that you would be crazy to pay more... and so the hype cycle continues!