I have one in a reef. I got this one very small, only a few inches, about a year ago. I got it for $250, but who knows what the pricess will do in the future. They were > $1200 two years ago and could easily go back that high if they only found a small area where they are/were plentiful. I have no idea what they go for now, but try to get the smallest available. They are not known to live very long, so the smaller you can get them the better off you will be. They will eat anything they can possibly get in their mouth. Mine has probably eaten $200 to $300 of fish (not feeders)! They also can be very expensive to feed. I have been unable to get mine on frozen.
-Steve