The trouble is that lots of women love the fact that they are pretty and that they represent a significant financial sacrifice for the man. (Scenario: "Honey, I bought you this $1,000 ring instead of the $5,000 ring because you can't put a price on love, right? Honey? Hello... No. Don't walk away!")
So I have a solution: the eco-ring!
First, it's a real diamond, but the diamond is fabricated in a lab.
Second, it costs as much to buy as a real diamond, but that price is composed of two parts. The first is the diamond and setting (say, $1,000). The second is a donation (say, $4,000) that the couple makes to various eco-organizations in honor of their marriage.
Third, the ring has a distinctive band or setting that tells others that it's an eco-ring. The setting also has a QR code (or similar) that allows one to look up what organizations they support. (The couple can keep the information private or share it or invite others to also contribute.)
What's needed to get the eco-ring off the ground? Publicity. A celebrity who chose this ring for their marriage would get a lot of people
So that's the idea. It's way better than the alternatives, so go for it!