I'll throw in my 2 cents on the subject. The ring I got my wife when we got engaged was less than 2k. She didn't want anything very large or expensive because in case anything happened to it, she said she'd feel really bad.
Now, throw that into the mix of the rest of the engagement process. We paid for our wedding ourselves, almost 40k, and bought our townhouse 4 months before the wedding with 20% down and bay area prices. Needless to say the "ring money" was needed in other places.
Truth is is she really loves you she won't be sweating you about a ring that's out of your means. I may have not gotten her the biggest rock, but I've been able to take care of everything else :thumbup: