TL;DR

Credit to...

Sale 1:

Sold for Stormy Storm Magistrate's Mullet and sweets here: http://prntscr.com/84e8d3.

Seller before: http://backpack.tf/profiles/76561198161706318?time=1439209615

Seller after: http://backpack.tf/profiles/76561198161706318?time=1439276400

Mini for Mullet:

Sold for a duped strange nuts'n'bolts private eye(15 keys).

Seller before: http://backpack.tf/profiles/76561198186210485?time=1437822618

Seller after: http://backpack.tf/profiles/76561198186210485?time=1437980400

13.5 * 0.9 = 12.15 rounded down to 12 keys

And now a mini inside the mini for the Private Eye:

Sold for an australium ambassador(15 keys)

Seller before: http://backpack.tf/profiles/76561198069892390?time=1437972715

Seller after: http://backpack.tf/profiles/76561198069892390?time=1437980400

15 * 0.9 = 13.5 keys

Price for sale 1:

12 * 0.9 + 10.44(Sweets) = 21.24 keys rounded down to 21 keys

Sale 2:

Sold for 22 keys pure

Seller's screenshots(Credit to dashie)

Proof of 22 keys: http://i.imgur.com/BDO4Kz5.png

Proof that it is stormy storm: http://i.imgur.com/nHjtLHV.png

Sale 3(Credit to randy: http://backpack.tf/u/76561198057521392)

Sold for 18 keys pure

Seller before: http://backpack.tf/profiles/76561198073742411?time=1435123677

Seller after: http://backpack.tf/profiles/76561198073742411?time=1435474800

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Final price: 21-22 keys

If you have any suggestions or tips, leave them below!