Sale 1:

Sold for Haunted Ghosts Familiar Fez

No outpost link available

Seller: http://backpack.tf/profiles/76561198141488279/#!/compare/1457769600/1457856000

Buyer: http://backpack.tf/profiles/76561198030050182/#!/compare/1457769600/1457856000

X = 27

Sale 2:

Sold for Green Energy Sola Topi

Seller: http://backpack.tf/profiles/76561198053547683/#!/compare/1453104000/1453276800

Buyer: http://backpack.tf/profiles/76561198032176942/#!/compare/1453104000/1453190400

X = 27

Sale 3:

Sold for C9 Counterfeit Billycock + Strange Pro. KS Knife (with parts) + 1.5 keys in items

http://www.tf2outpost.com/trade/27679129 - Offers

Seller: http://backpack.tf/profiles/76561198056364937/#!/compare/1452412800/1452585600

Buyer: http://backpack.tf/profiles/76561198053547683/#!/compare/1452499200/1452585600

X = 17.5 + 15 + 1.5

X = 34

Sale 4:

Sold with 6.5 keys in items for Searing White Russian

http://www.tf2outpost.com/trade/27987597 - B/O of 38

Seller: http://backpack.tf/profiles/76561198032176942/#!/compare/1459036800/1459123200

Buyer: http://backpack.tf/profiles/76561198072918306/#!/compare/1458864000/1459123200

Would rather use this to update the White Russian

Sale 5:

Bulk for Burning Scout Shako

Seller: http://backpack.tf/profiles/76561198083498744/#!/compare/1456387200/1456473600

Buyer: http://backpack.tf/profiles/76561198063604043/#!/compare/1456300800/1456473600

Sale 6:

Bulk for Secret Backbiter’s Billycock

Seller: http://backpack.tf/profiles/76561198063604043/#!/compare/1456732800/1456819200

Buyer: http://backpack.tf/profiles/76561198044684270/#!/compare/1456732800/1456819200

Sellers:

30 keys:

http://puu.sh/o1Bzr/94c95bfec6.png (2x) 14 days, 5 days

34 keys:

http://puu.sh/o1BAQ/dd5ca8848e.png - 1 month

http://www.tf2outpost.com/trade/27712412 - 2 months

http://www.tf2outpost.com/trade/28011662 - 2 days

Offers:

http://www.tf2outpost.com/trade/27065231 - 6 months

Sales at

27

27

34

34 is an outlier

Going with 27 flat.