To estimate the right cost of a pearl necklace you have to consider different traits: the experst generally agree that luster is the most important aspect to consider when buying pearls. Buy the pearl with the best luster, before insisting on perfect roundness, because is the quality of luster that gives the pearl its radiant glow and determine how light reflects on the many layers of nacre.
Good luster also implyes that the pearl will last longer because it means that the nacre is much more thick. Thin nacre in fact can quickly peel or spoil.
That’s why the experts usually base most of their appraised value (let’s say 70%) on luster. The 30% can go toward shape, since the possible shapes of a pearl can be manifold. Perfect roundness is quite rare, and rarity implyes hight price. Sometimes, on the other hand, a pearl can be not round but can have a fantastic luster, so to reduce the importance of roundness.
Since colour is a subjective factor and it’s not easy to objectively measure as luster or shape are, is considered relatively important.
Color is unique to the type of pearl, and is somewhat trend oriented. What may be trendy now may be out of style next year.
All of the mentioned factors go into the estimation of the cost of a pearl necklace. So do a little research and you will know how much that pearl necklace costs.