Good grief, I don't think I've ever seen so much bad dating advice in one place as the comments in this thread, lol.
This would be a fine comment if it were just the first paragraph and didn't begin with "Haha, grow up".
Much of that nonsense persists solely because so few possess the fortitude to resist it.
If your spouse insists upon a diamond, you may compromise, but also negotiate something of equal value to you. Perhaps, in exchange, you get sole authority to furnish and decorate the living room in any shared domicile, guaranteed.
You could install an octopus tank. You could put footballs on doilies on cinder blocks. You could create your own Batcave, Starfleet bridge, or Vault-Tec bunker. You could cover the walls in deep-pile maroon shag carpet. You could install 31.1 surround sound, using 24K gold Monster cables insulated with albino alpaca wool braids.
If the ring is a signal to your spouse's social circle that you are the best partner, so too is having all that embarrassing decor connected to the front door of the house, rather than hidden away in the basement.
If you have any inkling that particular compromise may be stupid and selfish, and not useful at all to the marriage as a whole, don't ask for a diamond ring.
A diamond is not forever. A 1:1-scale replica of the TARDIS in your living room is forever. If you burn a significant fraction of the family resources on a useless toy just for you, your spouse will be entirely justified in spending an equal amount on pointless toys just for them. And you can get a lot of pointless toys for the price of one ring--some of them will even yield a higher resale price.
If you don't want your marriage to be stupid and wasteful, you have to set a higher standard right from the start.