3 month old price!

Sale 1:

Sold for Disco Beat Down Pirate Bandana = 18 keys

[no outpost trade]

http://backpack.tf/profiles/76561198154469976/#!/compare/1454659200/1454832000

http://backpack.tf/profiles/76561198176860775/#!/compare/1454745600/1454832000

Sale 2: (can be used to update the little buddy)

Sold with The Caped Crusader for Cloud 9 Little Buddy

http://backpack.tf/profiles/76561198154469976/#!/compare/1454832000/1454918400

Sale 3:

Sold for Smoking Little Buddy + Orbiting Planets Connoisseur's Cap

http://www.tf2outpost.com/trade/27975856

http://backpack.tf/profiles/76561198045354273/#!/compare/1459036800/1459123200

http://backpack.tf/profiles/76561198044971268/#!/compare/1459036800/1459123200

Sale 4: (can be used to update the defiant spartan)

Sold with Purple Confetti Sergeant's Drill Hat for Cauldron Bubbles Defiant Spartan

http://www.tf2outpost.com/trade/27939782

http://backpack.tf/profiles/76561198044971268/#!/compare/1459296000/1459382400

Sale 5: (outlier)

Sold with Specialised Strange Frying Pan (~8) for Specialised Australium Scattergun (~38) = ~30 keys

http://www.tf2outpost.com/trade/27900770

http://backpack.tf/profiles/76561198090998026/#!/compare/1456560000/1456646400

Sale 6:

Sold with Overclocked Executioner for Energy Orb Professional Night Terror Scattergun (Battle Scarred)

http://www.tf2outpost.com/trade/27930911

http://backpack.tf/profiles/76561198048497407/#!/compare/1457337600/1457424000

Notes:

http://www.tf2outpost.com/trade/28028805 - B/O of 20 keys

http://www.tf2outpost.com/trade/27930911 - B/O of 20 keys

Conclusion:

One valid sale at 18 keys, in which two B/Os of 20 keys supports the drop. Taking a final flat price of 18 keys.

Feel free to support/counter my suggestion!