Clarions are actually quite aboundant. There are litterally millions of them. They are found all over the south pacific (mainly Mexico). They were illegal to harvest for around 10 years. This year (about 4 months ago) the Mexican government allowed a harvest of around 500 of these specimen (all under 7"). This was a legal catch and the fish went to collectors faster than they could be bagged.
Their price was around $5k per fish at the beginning. This ensured that you had a fish in hand.
Now that there has been another harvest of them, the price has dropped in half. They are still very rare in trade and that is due to the cost of harvesting them.
The license for harvest is big money, plus the boat out to the remote areas they are found, plus the nice increase in gas, plus the shipping back to the states.
Right now you can get one on another site for $2400. I would say within time you will be able to get them for $1000 or less.
It is all about supply and demand. Ask OPEC, they will give you an idea