Sale 1:

Sold for 13 keys

No outpost

Seller: https://backpack.tf/profiles/76561198044195191#!/compare/1500508800/1500595200

Buyer: https://backpack.tf/profiles/76561198198691921#!/compare/1500595200/1500681600

X = 13

Sale 2:

Sold for 11 keys

No outpost

Seller: https://backpack.tf/profiles/76561198065049657#!/compare/1499040000/1499126400

Buyer: https://backpack.tf/profiles/76561198208277691#!/compare/1498867200/1499126400

X = 11

Sale 3:

Quicksold for 9 keys

http://www.tf2outpost.com/trade/29198499 - B/O of 12

Seller: https://backpack.tf/profiles/76561198085654502#!/compare/1495584000/1495670400

Buyer: https://backpack.tf/profiles/76561198070775088#!/compare/1495584000/1495670400

X = 9

Sale 4:

Sold for Aces High German Gonzila + minor items

http://www.tf2outpost.com/trade/29194329 - B/O of 12

Seller: https://backpack.tf/profiles/76561198128297368#!/compare/1495324800/1495497600

Buyer: https://backpack.tf/profiles/76561198108021386#!/compare/1495411200/1495497600

Can be used to update the Gonzila.

Sale 5:

Bulk for Insomnia Kiss King

Seller: https://backpack.tf/profiles/76561198337244899#!/compare/1496188800/1496275200

Buyer: https://backpack.tf/profiles/76561198108613439#!/compare/1496102400/1496275200

Sale 6:

Bulk for Blizzardy Storm Executioner

Seller: https://backpack.tf/profiles/76561198108613439#!/compare/1497139200/1497225600

Buyer: https://backpack.tf/profiles/76561198094964657#!/compare/1497139200/1497225600

Sellers:

~11.5 keys:

http://i.imgur.com/ASF5Euq.png

https://backpack.tf/item/2306772970 - 8 days

13 keys:

http://i.imgur.com/n6qG1Oa.png

Sales at:

9

11

13

9 quicksold, excluding 9.

Going with 11-13.