Huh? 5x Arctic P12 is $24 on Amazon right now, no sale going on. And the whole Corsi-Rosenthal trend started specifically because consumer air purifiers were tested to be both noisier and less effective at their job.
But I'd honestly pay a premium for a commercial air purifier that just has a bunch of 120mm/140mm fan mounts instead of their "maybe tolerable at Very Low" integrated box-fan equivalent.
In general, all I've learned from online reviews of "quiet" appliances is that different people have very different definitions / criteria for "quiet".