When my sister got engaged her ring was very simple and cost $1500. Her fiance worked at the UPS store and they were 19, so that seems high to me for kids so young and broke. When my best friend got engaged, she split the cost with her fiance to make sure she got the ring she wanted since he didn't have a lot of money, and in the end the ring was about $6000.
I personally would rather not have a ring worth two months of my boyfriend's salary. I know you can get jewelry insured, but I lose everything, and I don't want to be a stress monster every day from wearing precious stones! I just want to enjoy something pretty on my finger.