Having owned the MEST 2 at one point, it definitely, far and away, set the benchmark for sheer clarity (and coincidentally resolution) but it’s also got a MSRP of $1500 which is a bit much for me in the end.
What other IEMs are clarity kings in the price brackets of:
Up to $100
Up to $400
Up to $700
Up to $1000
Just FYI the Mest Mk2 is still on sale for $999 (although they had said I think the sale would end on August 7th)
Thanks, I knew about it.
Unfortunately the MEST 2 will still be like $1200 minimum after it goes through customs to my country. I’m also not super keen on its tuning all things considered.
I’ll preface this by saying I’ll also assume you want the IEM to be decently tuned and so clarity isn’t your be-all and end-all requirement.
That said, it’s a pretty boring list as they’re all well-known, highly recommended IEMs:
Moondrop Aria - $80
7Hz Timeless - $200
ThieAudio Clairvoyance/Monarch - $700
Sony IER-M9 - $1000
The Sony isn’t necessarily more clear than the ThieAudio but it’s more coherent just remember to not use their tips as they are some matter of foam and absolutely butcher clarity.
Oh, the Dioko might actually be clearer than the Aria. Well, it technically SHOULD be. But I’ve not heard it and there’re not many impressions on it…
Good list, I’m surprised about the M9 however. I always read that it’s more like a warm DD with great tech and so I never thought it was a clarity champ 
Well, it IS warm. Which you can infer from the graphs without a demo. But it will appear overly warm with the included Sony tips. The best way I’ve heard it described is like a downgraded U12t and having heard both back-to-back, I very much agree with that. But it’s not much of a downgrade; it’s certainly not a $1000 downgrade. Soundstage is a bit smaller, dynamics are a bit less, bass is a bit less textured, and clarity is a bit less. Honestly, though, treble is better on the M9, IMO.
$100 - Olina and ER2SE
$400 - Timeless and Dusk
$700 - Variations and Monarch
$1000 - Monarch MK2 and S8 (smaller jump from $700)
Value wise I’d go with the Variations (amazing treble and bass texture), but it does come with the mid-scoop which is something you should taken into consideration. Great resolution, but not a meaty IEM.
Being an older set you don’t see it mentioned often anymore but some of the best clarity I’ve heard from an IEM is with my Etymotic ER4XR. I also own the ER2XR and prefer it for its smoother Bass presentation but for pure clarity the ER4XR is a Beast.
Hope this Helps 
Lasher
I love my Monarch, it just does everything right from EDM to rock.
Would love to listen to the mest, think it would be right up my street.
With the drop Collab coming out, this set may come back up front.