At the top end it's more about nuance and tuning.
- Do you have the library and DAC/DAP/Amplifier to drive your chosen IEM and does it synergise well with your own personal tastes, equipment and library.
- Different top tier IEM's play to difference strengths and preferences.
At the low end - well - there's the earbuds that used to come standard with the Sony CD players and EarPods.
$200 bring you the Apple AirPods Pro Gen 2
With wine, we have the WSET tasting guide to evaluate quality of an IEM. I'm uncertain if we have a similar evaluation standard. However,
very loosely:
Bass/Sub bass
Mids / Vocals
Highs/Treble/Extension
Detail/Resolution
Air/Soundstage/Placement
Overall tuning, balance and cohesion
Lower end IEM's will usually have significant deficiencies in several of the above.
As we approach $500 - 1000, loosely we may reach 50-80% of the way there. I used to be (and am still very happy) with my Andromeda 2020. They sound lovely with vocals, acoustic. Detail and soundstage were near the best in class in its day. But there is BA timbre and bass quality and impact is left wanting. You don't listen to dance/trance with the Andromeda 2020. But for what I listen to, it was lovely.
$2000 brings you IEM's like the U12 where many of the boxes are ticked and we are >80% of the way there.
$Summit-fi$ is chasing the end 5-10%. Some are more well rounded e.g. Trailli has a wonderful cohesion and can be enjoyed with most music types ; whilst others can be more polarising towards a certain tuning or genre. But you wouldn't expect significant technical deficiencies at this level.
As for value for money ; I suggest exploring the second hand market. Some bargains can be had. And you can ride the hype rollercoaster vicariously, wait for it to land. Popular IEM's purchased second hand usually can be sold on without too much of a loss.
We can probably apply a similar analogy to wine. It's rare to have a 'bad' $1000 wine provided it is in reasonable drinking window and stored well. But you may not appreciate the nuances and complexity of it ... unless you do. And if I told you this was Chateau Lafite ; there'll probably be a subconscious bias that 'this must be a stellar wine'. Whereas if I served it to my parents who drink Penfolds Koonunga Hill Shiraz and think its' the bees knees, it would be an absolutely torrid waste of time and money. My sweet spot actually is the Mt Edelstone Shiraz ($200 for reds ; but anything >$75 is usually very very acceptable) but other people would probably disagree!
I have slowly bracket crept up to the $2000+ mark - i.e. The Mest Mk III ticks a lot of boxes for me and purchased second hand for less ; represented really good value for money. Thank you (you know who you are!)