I buy gold, silver and diamonds for a living. It’s amazing how little we get for used diamonds with our wholesalers. If they are less than a 1/3 carat they bring very little. According to the best information, gem quality diamonds are as common as pearls. They bring a much higher price because DeBeers tightly controls and manipulates the market.
Rubies and Sapphires bring even less. A wise man buys one diamond in his life.
How much does the manufactured Ruby, Sapphire market impact that? A lot of what you see in Thailand now is manufactured.