A lot of people talk about the size of the diamond. It's the quality. You can buy a half a carat ring for thousands and buy a full carat for $400.
In the end who cares about the cost of the ring. She will get the house, kids, half of the savings, half your salary, and you will pay for college. You will move into a shit hole apartment and women will want little to do with you because you are broke. Most of your collective friends will side with her because you kept your mouth shut and she never stops talking about what a scum bag you are. Besides she is fun going out to clubs, restaurants and Vegas because she has money while you sit at the scum bag bar and have a crappy beer off the tap.
She will date and bang guy after guy before she settles with one. She will move in another guy into your house. He will sit in your favorite chair watching your big screen tv with an ice cold beer. Your wife who never let you fuck her up the ass will give it up all the time for the new guy. She will also swallow now instead of stopping when you get close. She will call you when the car or house needs fixing because it's for the kid's welfare. When you're fixing the car her boyfriend will open the window and ask if you want a drink. When you pick up the kids for your time she will be in the swimming pool you slaved to pay for with 5 of her divorced girlfriends who smirk at you with their almost college age boyfriends in the pool. One flashed her boobs at you and mouths the En Vogue song, "Never gonner get it."