White cultured pearl stud earrings with white Sapphire in 14k gold

White Cultured Freshwater Pearl Cluster Stud Earrings with white sapphire. set in sterling silver with 14k gold overlay Beautifully size and colour matched cultured pearls. The stud earrings are accented with a central white Sapphire Why is there such a difference between pearl earrings that may look similar? Generally it is the quality of the pearl , all other things being equal. Stamped 925 price firm, thank you.