Sale 1 :

Before : http://backpack.tf/profiles/76561198112732000?time=1437894000

After : http://backpack.tf/profiles/76561198112732000?time=1438671600

Sold for a Green Energy Buckaroos Hat : 28 keys

Mini on the buckaroos hat : http://www.tf2outpost.com/trade/26170454

Before : http://backpack.tf/profiles/76561198092396941?time=1434870000

After : http://backpack.tf/profiles/76561198092396941?time=1434956400

Sold for 28 keys

Sale 2 :

Before : http://backpack.tf/profiles/76561198100007274?time=1437202800

After : http://backpack.tf/profiles/76561198100007274?time=1437289200

Sold for a Disco Beat Down Wet Works : 23 keys

Mini on the wet works :

Before : http://backpack.tf/profiles/76561198083618753?time=1438671600

After : http://backpack.tf/profiles/76561198083618753?time=1438758000

Sold for a Circling Heart Shooter's Sola Topi : 26 * 0.9 = 23 keys

Sale 3 :

Before : http://backpack.tf/profiles/76561198038020646?time=1436684400

After : http://backpack.tf/profiles/76561198038020646?time=1436770800

Sold for a Haunted Ghosts Defiant Spartan : 24 keys

Mini on the spartan : http://www.tf2outpost.com/trade/26462735

Sold for 24 keys

Thus taking the range of 23 to 28 keys.

Supportivr criticism welcome