11 month old price!

Sale 1:

Sold for Duped Sunbeams Cyborg Stunt Helmet* = ~30 keys

http://www.tf2outpost.com/trade/27783564

http://backpack.tf/profiles/76561198048311062/#!/compare/1455264000/1455436800

Sale 2:

Sold with sweets (~4) for Collector's Rocket Jumper (43) = ~39 keys

[no outpost trade]

http://backpack.tf/profiles/76561198063640894/#!/compare/1457938800/1458025200

http://backpack.tf/profiles/76561198048311062/#!/compare/1457856000/1458025200

Sale 3:

Sold with sweets (~2) for It's a mystery to everyone Smokey Sombrero (33) = ~31 keys

http://www.tf2outpost.com/trade/27843040

http://backpack.tf/profiles/76561198225463104/#!/compare/1455350400/1455436800

Sale 4:

Sold for Australium Sniper Rifle (33) + 4 keys + sweets (~2) = ~39 keys

http://www.tf2outpost.com/trade/27860198

http://backpack.tf/profiles/76561198063796610/#!/compare/1457164800/1457251200

Sale 5: (can be used to price the bunsen brave)

Sold for Circling Heart Bunsen Brave

http://www.tf2outpost.com/trade/28031970

http://backpack.tf/profiles/76561198031350787/#!/compare/1459641600/1459728000

Mini-suggestion for Duped Sunbeams Cyborg Stunt Helmet*:

Seems to have sold for 29 keys + 16 ref = ~30 keys (HWAH was traded for the Cyborg which was traded for the pure)

http://www.tf2outpost.com/trade/27849391 | http://www.tf2outpost.com/trade/27783564

http://backpack.tf/profiles/76561198118621402/#!/compare/1455350400/1455436800

~ Taking a value of 30 keys.

Notes:

http://www.tf2outpost.com/trade/27783564 - B/O of 32 keys

http://www.tf2outpost.com/trade/27942441 - B/O of 34 keys

Conclusion:

Four valid sales at 30, 39, 31, and 39 keys. Taking a final range of 30-39 keys.

Feel free to support/counter my suggestion!