Ah, just read the article Anthony Calfo wrote on fad corals
Acans aren't all that "limitted" in the wild, but CITES makes them such to us as they only allow 1K wild a. echinatas and 2,304 maricultured a. echinata. They've been a non item for as long as I can remember as we've only gotten the semi nice looking ones for years. The internet turned US reefers with time and money onto the Japanesse reef tank sites and BAM, the fad begun. The limitted amount that is allowed to be imported, and the lack of species on CITES allowed, has driven a black market on smuggled corals unlike anything this industry/hobby has ever seen. That coupled with EBAY, and you get some major $$$$ players wanting to out do the next.
The market is getting FLOODED with acans from the Soloman Islands and Tonga as both aren't CITES members and don't adhear to their quotas. They do abode by their own fisheries quotas though.
Another reason for their sudden increase on the market is, many are brough in VERY large and fragged into many colonies that the hobbyist frag down even further. They do grow pretty quickly, so I doubt they'll hold the high price much longer.
Yah, micros are getting the same attention, but they go the same route. Scolymia was the last fad, and will be so again shortly IMO. They tend to run in cycles, just like fashion. I hear clam diggers are gonna make a come back
Many corals come from a much more limmitted area, and have even less amounts being brough into the US, but they don't commend the price of either a micro or acan. Their price is purely fad driven, nothing more, nothing less.