Look up the price of a blauberg Vento or a Lunos e2. They are ~$1800 CAD, and they get a fraction of the airflow. Computers have a large ecosystem behind them and have been in development for a very long time. This is still at the start of the deployment curve.

This has not answered my question. I can also come up with many examples of things that are expensive.

What does really inflate the BOM ?

And this is in no way to discount your effort or your results, I'm genuinely curious.

I have a spreadsheet where I track all inputs, and unfortunately it's just the cost of everything. The filament really doesn't help, but it also takes a lot of labor, and paying off the dev cost is also an important factor. Most of all, it's made in Canada where rent is expensive and I have pay that so I have to get paid a living Canadian wage.

I guess it is the cost of the exported externalities we are used to in western civilisation.

And imagine how higher the cost would be if everyone involved in the chain was paid a living wage, from mining to processing to logistics to to to..

Looks to me like a low cost version of the same could be designed with 2 CPU fans ($1), and a large 3D print ($1 - for the DIY version) or injection moulding for a commercial version ($0.30). Do time-sync between the units with grid frequency sampling (free), and have the whole thing controlled by a 2 cent microcontroller and a pair of triacs.

The whole thing, designed and made in China could probably come to a BOM under $4, and retail in the USA for $12.

While I agree with your points, $0.30 for injection moulding would need quite the scale, and I have doubts about whether two CPU fans would have enough power to flow enough air even in the absence of a HEPA filter.

Injection moulding is cheaper than you imagine now. The cheapest moulds start from about $250, and there are plenty of companies who will make a mould and make and ship 5k parts within 7 days.

These designs would need quite a few changes to be injection moulding compatible - for one thing the fins are probably going to have to be flat not circular due to draft angle requirements.

Changing the core to a roll of embossed steel foil might be a better bet, and whilst that would add about $1 to the price, it would also make the product work better and be more compact or more efficient due to a higher thermal mass in the core.

Got any links for the $250 moulds and companies ?

Maybe I could use them in my own project :)

Send these guys a message:

https://zhongshengmould.en.alibaba.com/

Never pay for a mould to be made with plans to ship the mould itself to another manufacturer - it's a common scam. Always make mould+make parts as a single transaction.

thanks !

You get similar ones from alibaba from around $175 : https://www.alibaba.com/product-detail/Fresh-Air-Ventilation...