Gold, silver, and diamonds are quite literally valued by an open market. You can call a broker and buy them for what the whole world has agreed is a fair price.

Gold, silver, and diamonds are quite literally valued by an open market. You can call a broker and buy them for what the whole world has agreed is a fair price. A piece of jewelry's wholesale value is determined by adding up the market value of its constituent components and then adding a workmanship premium. In an ideal world, consumers could buy and sell jewelry in the same way.