The super expensive CB for now so far is Hifiman RE10 (Planar Version), not counting the cosmetic luxury item out there, like beats diamond headphone (if this considered then closed wil be super expensive instead of open back counterpart), and not discontinued item (if we talked about sony r10 that's different story), but it seems there's no one tried making flagship e-stats closed back one so far, probably it's not suitable for closed setting, also those hifiman seemed not popular among audiophiles, the open back counterpart is more popular, like he1000 or susvara.
If we talked about sealed, well, ppl usually/tend to use IEM instead of CB headphone because of it, even there's an iem more expensive than TOTL closed back, in iem open back is somehow rare, that's why perhaps the reason, i conclude there's not many TOTL CB that actually success compare OB counterpart, the expensive most popular one is fostex CB and it's mod/variant in audiophille community compare to others, i;m not talked about SQ and preference, just their popularity in community in general, you can start to audition them to know why ppl choose them instead of open back counterpart, probably because there's something special that cannot found in iem or even CB one, for the reason, probably that's why fostex OB seemed not popular as their CB for example.
Because the world is noisy, basically. Pretty simple to understand. I'll take a close-back over an open-back for the most part at home because it helps me to immerse more in listening and avoid outside noises.
From his excellent closed back headphone thread, I believe that @Malevolent truly loves and prefer the closed back design. so, those people do exist.
For me, although I much prefer open back designs, I tend to stick to closed HPs when I'm around my wife. Even though I like to listen to music at low volume, my wife always thinks I'm blasting music as a result of sound leakage from the inherent design and constantly nags me for listening too loud even though I'm not.
To me, I would say true closed backs offer the "raw" sound quality as in you can hear every little thing, and the open back is the more refined/ smooth for music listening generally speaking.
Though you have closed backs that sound "open" but usually because they are vented so much which is a bit cheating b/c these "closed-back" high end leak which defeats the purpose sometimes like truly closed back ones .
I am definitely no expert on super expensive headphones of any type.
However, if you are a fanatic headphone person you need closed backs. For:
Noisy home (People talking, TV, etc.), traveling (plane, train, bus, car pooling, etc.), if you are lucky enough to be able wear headphones at work (during work, on lunch, etc.) And of course if you want to wear HP's in bed with a significant other.
As stated earlier I am not into super expensive headphones, but I coughed up enough for CFA Cascades, T60 Argons and Beyer T5's (3rd gen.).
IMO, open backs are best, but not always practical.
It's sort of like, why would a company put so much effort into a design that's inferior to begin with? All or most of the greatest headphones of all time are not closed, so it's strange that companies would use so much resources on them.