"Would you like a second opinion? Okay, here's a suggestion with proof!"

Credits to NICOLAS CAGE [even though his sale was nothing like he described in his suggestion]

The sales

Sale 1:

Sold for 15 keys pure:

http://backpack.tf/profiles/76561198162258442?time=1422885831 before

http://backpack.tf/profiles/76561198162258442?time=1423123200 after

-> 15 keys

Sale 2:

Sold for tflogo birdcage (~16.5) + pool party (3) + sweets (~0.6)

http://backpack.tf/profiles/76561198044449534?time=1428303600 before

http://backpack.tf/profiles/76561198044449534?time=1428409435 after

0.9*(16.5+0.6+3) = ~18.1, rounding to 18

-> 18 keys

Sale 3:

Sold for a gifted spec ks aussie axtinguisher (8) + a bud (12)

Buyer

http://backpack.tf/profiles/76561198115180487?time=1423036800 before

http://backpack.tf/profiles/76561198115180487?time=1423126993 after

Seller:

http://backpack.tf/profiles/76561198126553111?time=1423123200 before

http://backpack.tf/profiles/76561198126553111?time=1423123200 after

Buds history skipped an owner, it matches with the buyer of the aussie wrench:

history bud: http://backpack.tf/item/162011879

history wrench: http://backpack.tf/item/3434075319

0.9*8+12 =19.2, rounding to 19.

-> 19

The minis:

mini gifted spec ks aussie axt:

1:1ed to a regular aussie axt (8)

http://backpack.tf/profiles/76561198166294045?time=1425860911 before

http://backpack.tf/profiles/76561198166294045?time=1425884400 after

Taking 8

Sales at:

Final range: 15-19

Constructive criticism welcome!

~Foamy :3