I've always liked the idea of really simple wedding rings. Like, just a matching pair of gold rings without any diamonds or any of that crap on them. The whole point is that it's symbolic and that the true value of the marriage is the love each person has for each other, which is priceless. Why does it have to be symbolized with an expensive and largely useless piece of jewelry? Why should anything material compete with the value of the union itself?
In other news, I'm single. Can't imagine why...
For the most part this makes perfect sense.
I think part of the reason people get an expensive ring is because that seems to be the norm now.
Another part I find is that it might show commitment to the relationship for some people.