you need to catch up on lab-grown stones. Basically, they look better, keep their shine longer (i.e. no need to polish that often) and cost 10% of the "real one".
Just realize that intrinsic cost of diamonds is basically 0. Supply is artifically limited by De Beers and Co, demand is pushed up by shiny catalogues and stereotypes etc.
Now that many more labs are going to create moissanites and likes due to expiring patents, diamonds are going down the same path as pearls went ages ago (when people started growing them on mass scale).
So, my prediction is diamonds will lose at least 90% value in coming years, and lab-grown stones take over by storm, pushing overall bling-bling value even further down, making it as common as zirconia or stuff like that.
p.s. 2 of my first engagement rings were real diamonds, north of $5k value each. The most recent one is a custom made moissanite of better clarity and bigger size at < $1k. All girls were happy with their rings ;)