If she's smoking hot and out of your league, buy her an expensive one.
If she's rational and intelligent, don't buy her one; she'll understand how silly that tradition is.
If she's neither, what the heck are you marrying her for? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif