Per WDWMagic.com, tickets for Mickey's Not-So-Scary Halloween Party and Mickey's Very Merry Christmas Party are now on sale:
The cheapest advance purchase adult Mickey's Not-So-Scary Halloween Party ticket is $74, and the most expensive is $115.
For 2017, Mickey's Very Merry Christmas Party pricing begins at $89 for an adult advance purchase, up to $109 closer to Christmas.
You can purchase tickets for the Halloween party here and tickets for the Christmas party here.