Looks like a type of dottyback.
I know little about dottybacks so i may be wrong, but it has a similar body structure of a splendid dottyback.
I forgot to mention that Labracinus species are the largest dottybacks, growing to around 8 inches or so.
I have no idea, but they often turn up in stores so you should be able to get a ball-park figure from searching online. Here's a start: Dampiera Grouper, Spottysail Dottyback, Labracinus cyclophthalmus
Tony