Sale 1 : http://www.tf2outpost.com/trade/26751065

Sold for 13 keys

Sale 2 :

Before : http://backpack.tf/profiles/76561198103940513?time=1433228400

After : http://backpack.tf/profiles/76561198103940513?time=1433314800

Sold for a Smoking Surgeon's Stahlhelm : 13 * 0.9 = 12 keys

Sale 3 :

Before : http://backpack.tf/profiles/76561198080235153?time=1433228400

After : http://backpack.tf/profiles/76561198080235153?time=1433314800

Sold for a Circling Peace Sign Shooter's Sola Topi ( 13 ) but 2 key in items were added : 11 keys

Mini on the topi :

Before : http://backpack.tf/profiles/76561198154229385?time=1439622000

After : http://backpack.tf/profiles/76561198154229385?time=1439708400

Sold for 13 keys

Sale 4 :

Before : http://backpack.tf/profiles/76561198070461490?time=1433142000

After : http://backpack.tf/profiles/76561198070461490?time=1433228400

Sold for a Steaming Jumper's Jeepcap ( 12 ) + 3 keys in items : 15 * 0.9 = 14 keys

Sale 5 :

Before : http://backpack.tf/profiles/76561198122872975?time=1432969200

After : http://backpack.tf/profiles/76561198122872975?time=1433055600

Sold for the same Circling Peace Sign Shooter's Sola Topi as in sale 3 : 13 keys

Thus taking the range of 11-14 keys.

Supportive criticism welcome