Let's be honest brother there's a 50% chance that you will get divorced and she will keep the ring. What are you willing to pay for it now? Seriously though don't go blowing too much money on an engagement ring. If she wants or Demands a large ring your with the wrong girl anyway.
I'll give you my experience this was around thirteen years ago though. At the time I was making $400,000 a year before taxes and I spent only $7,500 on her ring. It's around two ct, back then money went further.
After we'de been together 10 years I turned around and bought her a ladies Presidential Rolex with over 400 diamonds on it. Cost was around $45,000. So my thinking is the longer we Stay Together the more expensive things I buy for her. At the beginning it's a crapshoot divorce could come from anywhere and my lady and I have had our share of problems. We could have been divorced by now as well but we've made things work just like any couple has to. You guys are going to grow apart and put back together if it's just the nature of the Beast.
My advice for what it's worth is at $60,000 a year go with the $3,000 ring, spend the rest of the money on your house if you both live together. You can always upgrade later as you live together longer. If you really want to stretch it take 10% of your income and buy a ring that's going to be $6,000 and way out of your budget in my humble opinion. Again like I said if this girl is really wanting a large ring and pushing for it you're with the wrong girl.