Last year the party on Halloween was around $80 - $85 dollars per person (can't remember adult vs child pricing), right? This year it's $105 per adult, $100 per child. Could be a couple things:
1.) They increased the quantity of tickets they are selling for the Halloween night.
2.) Less people have vacations planned for that time than historically, so there are less people "available" to buy the ticket for that party.
3.) They finally hit the cap on the price that people are willing to spend.
We shall see when/if the Halloween night sells out. I have a feeling it eventually will, but who knows!