I don't think oysters are rare though.

As for flavor, I can attest that good oysters have a distinctly nice (if acquired) flavor. Two to three chews, then a swallow. Served chilled.

Diamonds, on the other hand, only have a legitimate industrial use. As a "precious stone" they are not legitimate and only appear as such because of marketing and lots of terrible tactics. And for industrial uses, manufactured diamonds are superior. So this isn't really the same as oysters or other consumables.