Why are Akoya pearls more expensive than Freshwater Pearls?

Akoya pearl oyster grows in salt water, limiting the areas where farms can cultivate them, and can only grow 1-2 pearls at a time.

Freshwater pearls are grown primarily in manmade lakes and ponds in China. A single freshwater pearl mussel can also grow up to 32 pearls at a time, 16 on either side of the shell.

The reason why Akoya pearls are grown even though they are more expensive that Freshwater pearls - is that the luster, shape, and orient of Akoya pearls is superior to that of Freshwater pearls.