Once available, it will only be on sale until January 17th.
Alternatively, you can throw down $19.99 / €19.99 / £15.99 and get all six costumes and Frosty Blvd. in one big bundle.
The launch date for the holiday DLC will be announced at PlayStation Experience in Anaheim, CA this weekend; attendees of PSX will also have a chance to try out the new holiday content.