Costume Jewelry Values - How Are They Determined? They say diamonds are everlasting, and so are gold, silver and other gemstones. Any jewelry piece is perceived to be valuable. But how do you know the costume jewelry values when they are too flashy sometimes? Are they as worthy as your 500-dollar dress or expensive as you expect them to be? Costume jewelry is believed to be a vague collection in jewelry business. Determining costume jewelry values can be slightly cunning by ...