Wow, last suggestion had 84% :P

Sold for a CTFL thirst blood [worth 31.5 keys]

Proof: https://backpack.tf/profiles/76561198286234945#!/compare/1469577600/1469664000

The keys are not involved in the trade, look at the keys history.

Sale 2:

Sold for a Aces war pig+ Strange pro ks Quick fix [worth ~38,5 keys together]

Proof: https://backpack.tf/profiles/76561198286234945#!/compare/1469577600/1469664000

A big thanks to Randy for making this research

Mini for the Thirst

Sold for a Disco Noir

https://backpack.tf/profiles/76561198286234945#!/compare/1469750400/1469923200

http://www.tf2outpost.com/trade/28372978 - B/O of 27 would prolly cap at that

Mini for the War Pig

Sold for a Haunted Phantasm Jr Bone Dome - 28 Keys

https://backpack.tf/profiles/76561198055211132#!/compare/1471564800/1471651200

Sold for 29 keys - https://backpack.tf/profiles/76561198120760206#!/compare/1471219200/1471305600

Takin 28.5 for this.

So sale 1 would be 27 and sale 2 would be ~33 keys.

Going with the range 27-33.