One of the best air purifiers you can get (linked in the above writeup) uses PC fans and a custom controller where you can control the speed/volume: https://housefresh.com/best-air-purifiers-we-tested/#2-best-...
Those fans will not have sufficient static pressure to be useful. These makeshift purifiers may be great in a pinch (wildfire season and stores are all out), but far from the best.
Why is this so expensive? It's literally 4 PC fans and some plastic trays? I presume you bring your own filters.