Why is this hat unpriced

Sale 1:

http://backpack.tf/profiles/76561198040672259?time=1448784000&compare=1449129600

Appears to have sold with ~5.5 keys of sweets for a Flaming Lantern Tam O' Shanter

Tam O' Shanter Mini:

http://backpack.tf/profiles/76561198158335729?time=1448006400&compare=1448179200

Sold with 5 keys for Morning Glory Pure Tin Capotain

x = 23-5

x = 18

http://backpack.tf/profiles/76561198088877747?time=1448179200&compare=1448438400

Sold with 15 keys for a Burning Dread Knot

30-15 = 15

Using the average of 15-18, or 16.5

x + 5.5 = 16.5

x = 11

Using 11 flat. Feel free to tell me if I did anything wrong in the comments!