Sale 1:

Sold for Aussie Sniper Rifle + 5 Keys

http://backpack.tf/profiles/76561198147598816?time=1446710400

http://backpack.tf/profiles/76561198147598816?time=1446796800

http://backpack.tf/profiles/76561198147598816?time=1446710400&compare=1446796800

32 + 5

=37 Keys

Sale 2:

Sold for SF Sniper Rifle + S.Spec YER + S.Spec Direct Hit w/ Parts

http://backpack.tf/profiles/76561198147598816?time=1446624000

http://backpack.tf/profiles/76561198147598816?time=1446710400

http://backpack.tf/profiles/76561198147598816?time=1446624000&compare=1446710400

~ 14 x 0.9

= 13 Keys

Outlier

Sale 3:

Sold with Spec KS Kit + 1 Key for a GE Brigade Helm

http://backpack.tf/profiles/76561197995540052?time=1448265600

http://backpack.tf/profiles/76561197995540052?time=1448352000

http://backpack.tf/profiles/76561197995540052?time=1448265600&compare=1448352000

x + 13 + 1 = 52

x = 38

Mini for Spec KS Kit

Sales on SCM ~$31

Keys ~$2.47

= ~13 Keys

Taking 13 Keys

Mini for Brigade

Quicksold for 52 Keys Pure - http://www.tf2outpost.com/trade/27023131

http://backpack.tf/profiles/76561198047984178?time=1442127600

http://backpack.tf/profiles/76561198047984178?time=1442473200

http://backpack.tf/profiles/76561198047984178?time=1442127600&compare=1442473200

Taking 52 Keys

Sale 4:

???

Seller

http://backpack.tf/profiles/76561198212822380?time=1448265600

http://backpack.tf/profiles/76561198212822380?time=1448438400

http://backpack.tf/profiles/76561198212822380?time=1448265600&compare=1448438400

Buyer

http://backpack.tf/profiles/76561198108562502?time=1448265600

http://backpack.tf/profiles/76561198108562502?time=1448352000

http://backpack.tf/profiles/76561198108562502?time=1448265600&compare=1448352000

Not Using

Sale 5:

Sold for S.Pro Machina + S.Spec Festive Stickybomb Launcher

http://backpack.tf/profiles/76561198077819889?time=1443942000

http://backpack.tf/profiles/76561198077819889?time=1444028400

http://backpack.tf/profiles/76561198077819889?time=1443942000&compare=1444028400

~21 Keys after overpay

Outlier

Sellers:

http://www.tf2outpost.com/trade/27496574 - 40 Keys - 2 Days

~~~ Relisted from http://www.tf2outpost.com/trade/27411416 - 40 Keys - Unsold for 15 Days

~~~ Relisted from http://www.tf2outpost.com/trade/27320870 - 40 Keys - Unsold for 14 Days

~~~ Relisted from http://www.tf2outpost.com/trade/27247380 - 40 Keys - Unsold for 10 Days

Conclusion:

Sales at ~13, ~21, 37 and 38, taking a tight range of 37-38 Keys.