I spent less than $1000 on my moissanite engagement ring. Bought it in senior year of college. We're still together 10 years later and have 2 kids. If a girl really loves you, she doesn't need a real diamond. Her ring looks something like this one:
http://www.overstock.com/Jewelry-Wat...4&searchidx=32
I'm not saying you shouldn't buy a real diamond ring, but $50k is ridiculous.