Heya,
zenmaster10665, you should take a skim through this thread:
http://www.tfproject.org/tfp/showthr...ngagement+ring
(or do a full search for engagement rings on TFP)... there are a lot of people weighing in on how much is "proper", or "acceptable" to spend on a ring.
Personally, I'm of the mind that the two people involved should talk about what is really important about the ring...design, style, gem type and size, and of course, cost. If he's surprising her, well, then I guess all the communication is out the window.
In terms of how much should be spent, I've heard up to three months-worth. I'd be willing to bet that these guidelines are not set by anyone but the diamond and jewellery industry, not by concerned fiances/fiancees all over the world
