Pearls do something to the imagination. When you find one, you know it is so very, very rare to do so - so it is exciting because everyone knows "pearls are worth money".
In the case of quahog and food oyster pearls, people believe the smallest misshapen pebble is something Cartier would pay top dollar for. While quahog pearls found in the mouth show up here regularly, none of them has been big enough, or round enough, or purple enough, to bring in a good offer. I believe the owners of this one will gradually find this out.What they have is a good story, and if they put the pearl in a little cage to wear as a pendant, it will be a family heirloom for generations.
I lean toward the opinion that one is unlikely to find a sizable pearl in a commercial food clam. The biggest pearls used to come in the largest clams- too big for commercial fisheries' standard sizes, and probably rare in the wild nowadays. If there are still any big ones out there, they would have to be found by individuals in places not commercially fished.
Even when you find a small pearl like this, I have heard that they shatter upon drilling, which is why the little cage is necessary, though a prong setting might also work.