That is actually a great question! Jewelry is appraised at the weight of the metal plus gems, right. However value comes from history. For example, if you have great grandma's ring that she was given and she went through struggles and turmoil, specifically historically relevant events, that the ring survived. You eventually got that ring. The price to duplicate is x dollars, however, because of its history you are able to ensure it for far greater value, because the ring cannot really be duplicated anymore. The craftsmanship of that time, the methods of production, the history significance, cannot be duplicated.