The way you measure how valuable a diamond is? Purity. The way you tell a lab made diamond from a “real” diamond? Purity.
If it’s too pure it’s fake. There is this weird market where you want the purist diamond you can find, but not too pure. So you want some imperfections, just the perfect number of imperfections.
Too many imperfections and it’s low quality.
Too few imperfections and it’s worthless enough to grind to dust and use on consumable parts for power tools.
The modern jewelry market is also substantially different than what past generations taught me jewelry was. To them, jewelry was meant to be a value store. You purchase a valuable ring, the stone and metal held their value and you or your heirs could sell it later if times were tough.
Now jewelry seems more like buying a new car. It loses half its value when you drive it off the lot.