I personally wouldn't need a big, expensive rock on my finger. However, I believe that some traditions are healthy and bring us all a little bit closer together so we can understand each other better.
No matter how a tradition may have started, how we use it now is what's most important. I don't think that a fiancée or fiancé should EXPECT an expensive ring for their engagement. That seems really shallow. But there is nothing wrong with giving the person you're proposing to something that physically symbolises that promise you're making. That's how we use the tradition now; here's this ring, which is a visual reminder that I'm going to marry you.
Marriage, for me, is a very big step in one's life and a very important promise. So giving a ring, no matter the cost, seems like a worthwhile thing.
Are big expensive rings overrated? I would say yes. But the tradition at its core is something I would like to see continue, well, forever. :)
