I agree they are hard to find, these didn't get a wide distribution and they came out at a time when G3 was plummeting in popularity. The Ponyville mermaids were kinda a last-ditch effort to drum up some interest. I never see them come up in ebay lots of pony stuff.
Kinda like Mimic, ya know? No one much wanted them when they were made, now they're hard to find since not a lot of collectors got them to resell.
halicabi, awesome photos! I've never seen a complete set together, before!