9 month old price!

Sale 1:

Sold for Aces High Brown Bomber = 34 keys (B/O caps it at 33 keys)

http://www.tf2outpost.com/trade/27974180

http://backpack.tf/profiles/76561198114318692/#!/compare/1458950400/1459036800

Sale 2:

Sold for $72.20 via PayPal = 72.20/1.9 = 38 keys (keys were valued as 1.90 USD each in this trade)

http://www.tf2outpost.com/trade/27900360

http://imgur.com/a/gyfPX

Sale 3: (can be used to update the GE counterfeit billycock)

Sold for Green Energy Counterfeit Billycock + sweets

http://www.tf2outpost.com/trade/27939302

http://backpack.tf/profiles/76561198087968709/#!/compare/1457596800/1457683200

http://backpack.tf/profiles/76561198076496148/#!/compare/1457596800/1457683200

Sale 4:

Unable to identify sale but had a B/O of 32 keys

http://www.tf2outpost.com/trade/27963889

http://backpack.tf/profiles/76561198140468405/#!/compare/1458284400/1458370800

http://backpack.tf/profiles/76561198028490870/#!/compare/1458370800/1458950400

Sale 5: (outlier)

Sold for 25 keys + sweets (~1.3) = ~26 keys

http://www.tf2outpost.com/trade/27953362

http://backpack.tf/profiles/76561198076496148/#!/compare/1458111600/1458198000

Notes:

http://www.tf2outpost.com/trade/27963889 - B/O of 32 keys

http://www.tf2outpost.com/trade/27974180 - B/O of 33 keys

Conclusion:

Two valid sales at 33 and 38 keys, as well as B/Os supporting the range. Taking a final range of 33-38 keys.

Feel free to support/counter my suggestion!