It's sad that American culture assumes that the man who spends $10K on a ring loves his fiancée more than the man who spends $500.

Several companies that produce diamond alternatives, such as lab-grown diamonds and silicon carbide stones, are growing and rapidly expanding their product lines. I think the reason for this is that people are questioning the wisdom of spending a ton of money because marketing campaign have told them they must if they love their partners.

That presupposes that marriage is solely about love, which is itself an odd and mostly western concept.

Marriage is, just as much, an economic arrangement in which people make often very significant sacrifices in order to create a household and potentially raise and support children. It necessarily entails a significant commitment on both sides, including the commitment to stick with each other in the case of hardship or sickness. When you account for that aspect of marriage, it makes total sense to require some showing of financial wherewithal.

And the recipient of the ring should be able to redeem the value of the backing investment after a certain time.

Worth a business attempt? Hmm.

I think you'd want it to work kind of like a cashier's check. If you have the ring and your identification matches what's on file, then cashing out your investment is easy. If you've lost the ring or you're not the primary on the account, there are delays (of perhaps months) but cashing out is still possible.

But personally I don't see why anyone would care about a $10k ring. Different cultures, I suppose.