I have to bring this up because a lot of people are talking as if this is the entirety of the reason for their decrease. But there's diamond files, diamond cutting blades/wheels/drills, you can make glass from it (really only used in labs that absolutely need them because the price), and many more uses. Many of these don't care about size, quality, or clarity. So instead of pulling from scrap material from jewelry making or rejected diamonds you could just make your own and ensure your own supply.
One of the things I've loved about synthetic diamond prices coming down is just how cheap and available diamond cutting wheels and filing tools have become. You can now get a set of diamond files on Amazon for under $10. That's crazy