For thousands of years, pearls and other shells have been valued by the human race. Shells were sometimes used as a form of currency in some cultures. I must assume that only the rarer shells were used that way, otherwise everyone would have been rich...........LOL.
Pearls are formed by oysters when they get a bit of sand in their shell and can't seem to get it out. They form a protective coating around the sand because it is irritating to them. Over time, the pearl gets larger and larger. A "cultured" pearl is created by putting a large bead in the oyster and letting it put a few coats of "pearl" around the plastic. You can see that natural pearls are considered much more valuable than "cultured" pearls. Natural pearls are often called "wild" pearls.
Abalone has its own special value. It is the shell you often find inlaid in all kinds of items. See the photo below:
The pearl necklace below is a strand of cultured pearls from scott kay jewelry and is priced at nearly $2K. It is apparent that pearls prices are not based on their original location or if they are cultured or not but the price is merely where they are bought from.