Sale 1:

Sold for Purple Confetti Stout Shako (18) + 1 key

No outpost

Seller: https://backpack.tf/profiles/76561198050813027#!/compare/1496448000/1496534400

Buyer: https://backpack.tf/profiles/76561197968968337#!/compare/1496448000/1496534400

X = 19

Sale 2:

Sold for Stormy Storm Ye Olde Baker Boy (18) (ID’s match)

No outpost

Seller: https://backpack.tf/profiles/76561197968968337#!/compare/1496793600/1496880000

Buyer: https://backpack.tf/profiles/76561198068306039#!/compare/1487462400/1496966400

X = 18

Sale 3:

Sold for 13 keys (probably to a buy order)

Seller: https://backpack.tf/profiles/76561198015384426#!/compare/1499731200/1499817600

Buyer: https://backpack.tf/profiles/76561198054758757#!/compare/1499731200/1499817600

X = 13

Sale 4:

Bulk for Haunted Ghosts Tyrants

Seller: https://backpack.tf/profiles/76561198074924284#!/compare/1498694400/1498867200

Buyer: https://backpack.tf/profiles/76561198061665716#!/compare/1498694400/1498867200

Sale 5:

Bulk for Blizzardy Bonk Boy?

Seller: https://backpack.tf/profiles/76561198241107714#!/compare/1498694400/1498780800

Buyer: https://backpack.tf/profiles/76561198314168660#!/compare/1498694400/1498780800

Sellers:

18 keys:

http://i.imgur.com/boapJct.png - 11 days

http://www.tf2outpost.com/trade/29255417 - 2 weeks

Sales at:

18

19

Going with 18-19.