I spent a lot for her diamond but I absolutely got the most for my money. I was careful to research the market and ensure that I got the most diamond for the money. After going to a lot of the normal retail stores - Tiffany's, De Beers, leading local jewelry stores, as well as the San Francisco Diamond center and even Blue-nile online, I settled on a well respected wholesaler in the nob hill district of San Francisco. People I know who don't need to worry about money use him. I found that he was able to get me a diamond at about 60% of the price of retail. If I had bought my ring at Tiffany it would have easily been double the price and maybe more. In the end, I was able to get a GIA certified and inscribed princess cut diamond with the following specs: 2.2 Carat, F grade color, VS2 grade clarity, and with table size and depth in almost perfect balance, enabling maximized sparkle (this is an important detail to look for in a diamond, as it increases its presence, enabling even a smaller diamond to look bigger.)
My advice to anyone looking for an engagement ring is, don't be lazy and just go into a store and drop the money because you can get a lot more for your budget if you are judicious and thoughtful about it. Start early, do your homework, take your time, and don't make impulse decisions. Also, use blue-nile to bargain your price down. They make a great iPhone app that can save you thousands when bargaining.