And for good reason. Noctua actually stays completely silent at lower RPMs, unlike the fans you mentioned.
There's a place for each type of fan, this one is better with silence than a screamer.
Only the IP67 are waterproof and dustproof, which is what ehume reviewed.
Not all deltas or sans ace fans are screamers. I dont understand why thats so hard for you to process. the AFB line goes down to 1700 rpm if I remember correctly, and Sans ace undervolts better than some fans PWM, most control software allows 1% increments so I dont see that definition of control as a problem.
If you cant stand the sound of ball bearings and need a fan with a modified rifle bearing then by all means spend the money on Noctua. Youre exactly the kind of person they want to capitalize on.
I have a hard time fathoming how sensitive people are to bearing noise, then complain when their system runs hot because the fans are running so slow.