But that doesn't dictate how much you're supposed to be paying for each individual diamond. If you have a "proof of love" budget of $6000 you could just buy five used diamonds instead. You could then start an arms race with other married couples and claim they don't love their spouses, because they only bought them a single diamond.

Edit: I checked and multi diamond cluster rings look way more impressive and make single diamond rings look cheap and icky.

Theoretically you could spend the same amount an some insanely huge used diamond.