Sale 1 :

Before : http://backpack.tf/profiles/76561198045309178?time=1439276400

After : http://backpack.tf/profiles/76561198045309178?time=1439362800

Sold for a Strange Professional Killstreak Frying Pan, sales average at 16 keys on classifieds : 16 keys

Sale 2 :

Before : http://backpack.tf/profiles/76561198144204423?time=1438930800

After : http://backpack.tf/profiles/76561198144204423?time=1439017200

Sold for a Blizzardy Storm Cadaver's Cranium : 14 keys

Mini on the cranium :

Before : http://backpack.tf/profiles/76561198144204423?time=1439362800

After : http://backpack.tf/profiles/76561198144204423?time=1439622000

Sold for a Strange Professional Killstreak Australium Axtinguisher : 14 keys

Sale 3 :

Before : http://backpack.tf/profiles/76561198160297463?time=1438239600

After : http://backpack.tf/profiles/76561198160297463?time=1438326000

Sold for an Aces High Whirly Warrior ( 17 ) + 1 key : 17 * 0.9 + 1 = 16 keys

Thus taking the range of 14-16 keys.

Supportive criticism welcome