I saw the Youtube video of this a month or two ago. I forget where the reference came from.
The units can be assembled in around 15 minutes, last for months, and cost between US$50 and $150 in materials
My view - if you want an air purifier, just pay for a real/smart unit - they are not very expensive (same price range or slightly higher than what is stated above depending on model - certainly not 10x) and will provide more utility than this DIY version. This DIY version is not going to provide any indication of the air quality, while the smart ones do. A real purifier will come with some efficient design so you can place it on a night table, coffee table, or a convenient location and will look aesthetically pleasing. A real purifier will also come in various sizes appropriate for how large a room you're using it in.
The nice thing with the real/smart air purifiers - they are "smart". They can automatically come on if they sense air quality is deteriorating. You can set up rules, timers, schedules, etc. like other smart devices. The speed at which it runs is also selectable manually or through the app. Ours also have a sleep mode, where the fan speed goes very low and provides some low volume white noise, which is really great when sleeping.
The smart purifier also tells when it's time to replace the filter. With the DIY version, you really have no way of knowing when it's the right time. When you decide it is time, you need to completely rebuild it.
My belief - as indicated in the wiki link - it was really a quick and dirty solution/alternative for those stuck at home during Covid. In the long run, I don't believe this DIY version is going to save much money and you really don't have a good indication of how effective it is without buying an additional sensor.