The price of blue sapphire gemstones depends mainly on the color, clarity, and natural inclusions. Blue sapphires with no natural inclusions are rare and fetch extremely high prices. Kashmir blue sapphires, considered the best, can sell for amazing prices, with royal blue untreated Kashmir sapphires exceeding $1500 per carat. On average, natural unheated Ceylon blue sapphires sell for $100 to $400 per carat.