Steve,
I want to apologize for the delay in responding to your post. The Masked Angelfish- Genicanthus personatus is the rarest member of this genus in the aquarium trade.
Like numerous other species that are sought after by a few seasoned veteran fish enthusiasts and collectors, the reason that this fish is rarely seen is due to its limited range, and depth where theis species is normally found, which is over 210 feet in Hawaii (apparently some of these fish at Midway are seen in shallower water).
The biggest reason that we do not see this fish available took place in 2006, where President Bush had designated the Northwestern Hawaiian Islands a US national Marine Sanctuary which covers the entire normal range for this species. Interestingly enough, this national marine sanctuary is the larges in the world, and covers over 140,000-square-miles. It is illegal to harvest or fish for marine ornamentals in the Marine Sanctuary.
Additionally, accessibility to the NW Hawaiian Islands and Midway is very difficult, with Midway being a Military territory. All visitors that plan on diving, snorkeling, or even just wishing to take photographs around the islands must obtain a permit. It is illegal to fish or harvest species for the aquarium trade in this territory.
Here on ReefCentral.com, Angelfish guru and friend John Coppolino (copps), posted a thread about an incredible adventure he was a part of that took place in October of 2007 on the big Island of Hawaii. While diving with one of his friends who is a very experienced diver/collector in Hawaii, a Genicanthus personatus was legally collected in waters which are outside of the fishes normal range. This rare occurrence along with the fish’s journey was documented here on RC, so if you get some time, please try and search the archives for more info on this fascinating adventure.
In the end, I believe the fish was eventually sold to one of the largest, and most well known stores in Japan, with a reputation for offering the most rare and unusual marine fish species available in the world.
If this fish were to ever become available again it would have to be legally collected in waters outside of its normal range. I would imagine the retail price for this fish would be around $10,000 US.
Happy Fishkeeping!