Not the same thing, but you can get diamond tipped 3d printer nozzles for ~$100: https://www.amazon.com/Diamondback-Nozzles-Compatible-Polycrystalline-Efficienc

Not the same thing, but you can get diamond tipped 3d printer nozzles for ~$100: https://www.amazon.com/Diamondback-Nozzles-Compatible-Polycrystalline-Efficiency/dp/B09LLWY2YK https://www.amazon.com/Diamondback-Nozzles-Compatible-Polycr... Considering that these are a niche product requiring a precisely shaped diamond insert made by a relatively small operation in the US, I think it's believable that a Chinese company could produce diamond files for ~$10, considering that it only needs diamond powder and has more space for mass production.