Then I imagine part of it is the fact that people are willing to spend $x on a fan (of any sort) and $x+y on an air purifier. If an air purifier is generally a

Then I imagine part of it is the fact that people are willing to spend $x on a fan (of any sort) and $x+y on an air purifier. If an air purifier is generally accepted to be a higher-price item, then making a fan into one with some sort of filter helps justify the higher price. (Just speculation, though. I have no info about their design or marketing decisions.)