these are wild from tuamotu, french polynesia, tahiti, all one in the same. they do not harvest them till they are at least 5" and I have been looking at these for a while online and researching them.
An article I read said the locals eat 100,000 pounds of meat from these clams every year. That has got to be a lot of clams. The on-line vendors are selling in the $200-500 price range each so when I saw them on e-bay I jumped on the chance, but I will have to wait and see how that pans out.
You can research these and find they come in a wide variety of colors and patterns and are stunning but large and expensive.