Diamonds were never a luxury. They were a trinket, a shiny, that used to take hoardes of slave labor to extract out of the Earth's crust. Now we can grow them in a lab, and can be higher quality than the "natural" ones, for cheaper, without the slave labor. Outside of their use as an abrasive, gem-quality diamonds have few if any uses outside of "ooooh, aaaah", much of which is a product of their perceived rarity and prestige perpetuated by De Beers' marketing.

De Beers should be having a moral and ethical reckoning, not a financial one. They should be happy they get to keep any of their ill-gotten wealth at all, let alone that the fucking gravy train is running out. Eat shit. Sorry asshole, the business is dead. Get over it.