Most couples rely on their income to pay their bills and you also may want to consider other big purchases that will coming up. If your goal is to buy a house right after your wedding or even before, that's a big expense.
Your soon to be fiance no longer has to decide on the budget alone. If realistically they can only spend $1500, you can still get a gorgeous ring for that price tag. If money is tight, you can always get a smaller ring now with promises that on your 10th or 20th anniversary, you'll get an "upgrade ring." By that time you'll be too attached to your current ring anyway!
A good rule of thumb is to ask her friends for suggestions on what type of ring she would like. Most girls in this day and age have a Pinterest board filled with rings they like that typically fall within one or two styles to narrow down your search.
Another alternative if you have this possibility is to use a family heirloom. Not only does it mean more because it's been in your family and passed down; You can also (with your family's permission) give the ring an upgrade and add to it so it is partly your family and partly your new life together.
Whatever you decide to do, know that your new fiance will love it no matter what because it came from you!
Photo by Selcouth Creative