>All those things plus some fancy instagram marketing is tricking people to spend $700+ on an air filter.

I think there is also the middle ground of spending about $150 on an air filter, because the ones from Ikea and Bluair look and sound much nicer in my home than a box fan with a HEPA filter duct-taped to the front.

I don't mind the repeated breathless excitement over it. It feels very on-brand for hackers to get excited about discovering a cheap and ugly DIY version of a commercial product and apparently miss that not everyone wants one in their kitchen.