The balls aren’t that hard to make [1], but doing so at scale economically isn’t something you can build with some plug and play off the shelf machinery. It takes years to assemble a functioning factory like that and tune the process before it’s profitable. All the Western companies that make them are decades old with established and largely paid off manufacturing lines but once the Chinese government decided it was a critical industrial product downstream from their five year plans, it was just a matter of time and capital. Few other governments are willing to subsidized specialized manufacturing like that so investors don’t want to risk entering an established market.

The hard part is really quality control when making hundreds of thousand or millions of balls a day, at which point all metrology equipment is basically useless except for random sampling, which means your process has to be pretty much perfect before anyone will even buy from you, but you cant slow down the process because then you’re just losing money.

[1] https://youtu.be/41Z5v4NybWA?si=xzFw2xD93D9TfW6F (process for the balls starts around 1:50)

>Very small, high precision spheres are hard to make

I remember this was on a list of zero-g manufacturing techniques that NASA was investigating at one point. I wonder what became of that? Normally, I'd think the cost would be prohibitive, but you can probably fit a lot of 0.1mm ball bearings in a ton of cargo.