For value assessment, depends on the metal used as in bronze would be more valuable than iron . Secondly, the amount of craftsmanship that has gone into the creation of the piece. Thirdly, the age of the piece of art. The older it is the more valuable. One aspect that does add heft to the price is, if the item has a special history behind it, it terms of the legacy of the earlier owners. All these factors go into assessing the true worth of an object of art. Hope you find these markers useful