Diamonds aren't worth much because they're actually not that rare. The only reason they command the price they do now is because of the De Beers cartel.

The "diamond alternative" meme is becoming increasingly popular with our generation, such that I predict that in a few generations nobody will care to buy "real" diamonds for engagement purposes. When this happens, the price of diamonds will fall dramatically (if it hasn't already by that point).

Diamonds are so overrated.