you know they’re used as a cutting tool

Natural diamonds aren’t even rar, it’s just one big business family owning pretty much every mine on earth. Even jewelry diamonds could be very cheap without artificial price manipulation.

However they’ll use artificially produced industry diamonds for CPUs. Since they’ll be very tiny and purity probably doesn’t matter too much, this is likely a relatively cheap process too. I doubt they’ll want to lose on revenue.

Is carbon not abundant?

It’s not as if they’re using diamonds hand-mined by children in Africa or something… That’s the jewelry market. Synthetic diamond is in a ton of stuff, and it’s not really that expensive. The “material” is just carbon.