That might be true. However, again, why should a "perfect" diamond cost so much more than a regular industrial one? What makes it so special? Size? There's industrial diamonds of that size. That it lacks impurities and microscopic cracks? Well I won't really be able to see most of those anyway, will I? So they don't really matter.
I see you don't agree, but for me, a perfect diamond could never be worth more than industrial ones. Oh, is it worth more because it's set in a ring? Sure. But not 100x times more.
I actually have a friend who started a business as a jeweler, she doesn't work with diamonds but she does work with some other precious stones, most notably rubies and sapphires. She makes nice looking pieces and she indeed require years of training. But even she can agree that some stones are over-rated. It all depends on what the person likes. There's people liking diamonds on platinum settings and some liking a regular preety stone on a steel setting.