Nightmare moon and minty are still running pretty high on ebay, $30-35 for NMM, $15-25 for minty, so I'd say around $70-$100 for the set depending on the buyer if it were an auction, I honestly couldn't be that much more specific. Hula hula has been hot for a while now, she could easily fetch up to $12 at the moment, lots of people seem to be looking for her, and she's easily the most sought after of the set. $6 sounds about right for beach ball, she seems to sit pretty low unless she's absolutely mint, then she goes a fair bit higher.