The microprocessor costs about £20 (though you can get off brand ones for much cheaper), the flexible array costs between £5 and £10 depending on where you get it from (if you can wait for shipping from china!) and lipstick batteries are very cheap these days. The LED mask that I bought but didn’t end up using cost £40, which I’d imagine if the masks were to be mass produced is about what the whole system could cost. Then there’s the Azure subscription and the Ably subscription, which are both honestly incredibly cheap, I’m on the free tiers and haven’t even touched the sides yet!