I presume you’re talking about De Beers (as this is such an often repeated meme)? Their market share is ~23%.
https://www.statista.com/statistics/585450/market-share-of-d...
They’re also quite tightly regulated by the EU, and since 2006 have been prohibited from buying stock from Alrosa (the actual largest diamond supplier in the world). So their scarcity is most certainly not artificially maintained by De Beers, as people so often like to claim.
See e.g. https://www.businessinsider.com/history-of-de-beers-2011-12?...
You’re also quite narrowly focusing on the romance angle (which is the result of successful marketing, not artificially induced scarcity). I don’t think Quavo wears an iced-out AP as a symbol of love, for instance.
The artificial scarcity argument simply defies logic. The entire worlds supply of natural diamonds was created hundreds of millions of years ago, and the earth is done making them.
Your argument about their scarcity being artificial also seems pretty flawed to me. Naturally occurring diamonds are genuinely scarce, and most people value them differently from lab created ones (as they are free to do). Perhaps those people are just being stupid, but they’re no more stupid than all the other people in the world who find value in useless things. It’s not illegal to make lab made diamonds, they’re freely available on the market. But just like a pixel-perfect print of the Mona Lisa, they’re not valued quite as much as the real thing.