This ties into the Rarity factor as well. The difficulty involved in nucleating a batch of saltwater Akoya pearls is very high. The Akoya oysters are sensitive little guys, and must be treated oh-so gently to prevent them from either rejecting the bead nucleus or dying outright after the grafting procedure.
Basically, what I’m saying here is that there’s a LOT more blood, sweat and tears that go into the creation of even just a single Akoya pearl over their Freshwater cousins. The risk is high for everyone – oysters, farmers, processors and auctions. Higher risk = higher price.
With Freshwater pearls, the only nucleus needed is a 1.0mm square piece of donor mantle tissue, inserted into the soft body of the mussel, so it’s an easier process (again, with a LOT more insertions equaling a higher amount of pearls per harvest). The man-made lakes and ponds used to culture the pearls are less subject to Ph balance disruptions, temperature fluctuations, algae blooms and pollution run off from the coast.
Overall, it is a less risky proposition to produce Freshwater pearls (although please note that I’m NOT saying it’s NO risk – Nature is wild and unpredictable no matter how hard we try to control conditions anywhere).
But again, less risk = lower pricing.