Needs a bump! :D

Classifieds - http://backpack.tf/classifieds/?item=Festive%20Knife&quality=11&tradable=1&craftable=1

5x 13 keys

8x 14 keys

http://www.tf2outpost.com/trade/24161884 - 13.6 keys

Sold: http://www.tf2outpost.com/trade/24098387 - 14 keys

Selling below 14 keys

http://www.tf2outpost.com/trade/23779580 - 12.5 keys

http://www.tf2outpost.com/trade/24164878 - 13 keys

http://www.tf2outpost.com/trade/24121566 - 13.25 keys

http://www.tf2outpost.com/trade/24072281 - 12.5 keys

http://www.tf2outpost.com/trade/24161166 - 13 keys

http://www.tf2outpost.com/trade/24127224 - 13 keys

Unsold for 14 keys

http://www.tf2outpost.com/trade/24139316 - 1 day

http://www.tf2outpost.com/trade/24142189 - 1 day

http://www.tf2outpost.com/trade/24122051 - 2 days

http://www.tf2outpost.com/trade/24141904 - 1 day

http://www.tf2outpost.com/trade/24039600 - 1 week

http://www.tf2outpost.com/trade/24159971 - Young

http://www.tf2outpost.com/trade/24033421 - 1 week

http://www.tf2outpost.com/trade/24019328 - 1 week

http://www.tf2outpost.com/trade/24153379 - 1 day

13 keys seems the most common selling point besides the unsolds of 14 keys but as I did find a sale at 14 keys and a quite a few were young it is best to keep it in the range! :D