This should have been 12 keys flat.

Classified ads at the time of posting:

http://m.imgur.com/4Citf1P

http://backpack.tf/classifieds?item=Festive+Sniper+Rifle&quality=11&tradable=1&craftable=1

1*11 keys

6*12 keys (2 have Specialized Killstreak, 3 have Killstreak and 3 have parts attached)

Unsold at 12 keys and 8 refined (~12.5 keys):

http://www.tf2outpost.com/trade/26399024 (~2 weeks, poorly bumped)

Sellers at 12 keys:

http://www.tf2outpost.com/trade/26477045 (Has Killstreak and Airborne Enemy Kills, ~1 week old)

http://www.tf2outpost.com/trade/26454826 (~1 week old)

http://www.tf2outpost.com/trade/26554432 (Has Headshot Kills and Medics Killed That Have Full Übercharge, young)

http://www.tf2outpost.com/trade/26498576 (~5 days old)

http://www.tf2outpost.com/trade/26522405 (Has Specialized Killstreak, ~3 days old)

This is all I could find on Outpost that are valid at the time of posting this suggestion.