DeBeers should be shitting themselves. Those shameless bastards have manipulated the market for so long that they fully deserve to be undercut. But, I think if women truly didn't care, then the mark DeBeers puts on mined diamonds wouldn't work. So far, it seems to be working fine for them, as they are still in business when they really shouldn't be, given how cheaply diamonds can be made.
Cubic zirconia refract less than diamonds - so they have less "fire." Worse than that, CZ are always cut like diamond so their angles are wrong for their chemistry. Moissanite actually has a higher index of refraction than diamond, but again, you have to cut for that index of refraction. So a moissanite cut to take advantage of the fact that its a moissanite doesn't look anything like what we're used to diamonds looking like, so you have to sell it as if it's awesome all on its own. And since it's nothing but silicon carbide, any markup is a retarded markup. Synthetic diamond is its own thing. Nobody makes "fake" sapphires and rubies any more because creating synthetic corundum is child's play. It can be done in such industrial capacity that the window you pass your cans over at the checkout stand is synthetic sapphire. The gem industry makes fake topaz - which is quartz - out of real sapphire. It's cheaper than digging up topaz for class rings'n'shit. Large-scale production of gem-quality diamond will change the world much the same way large-scale production of gem-quality sapphire did. After all, the Soviets were fucking around with it in the first place because it makes a bitchin' substrate for integrated circuits.