My philosopy is the thought. I mean whether you spend $200 or $20000 on an engagement ring, she should still love you no matter what. I'm in college and so is my gf, I spent about $250 for hers. It was a $600 ring, but was on sale(there is a hell of a markup on jewlery). It's not the most expensive or nicest ring in the world, but it gets the point across that I want to spend the rest of my life with her.

Just my .02