Alright, 1st unusual suggestion of my own. Here goes.

Sale 1 (mine)

Sold for Strange Awp and 26 ref in items, + 2 ref = 12 * 0.9 = 11 keys

http://i.imgur.com/1lwIHXz.png?1

X = 0.9*11 keys + 0.9*26 ref + 2 ref

X = 10 keys + 25 ref

X = 11.25keys

Sale 2

Sold (same day) for S. Spec KS Festive Knife (Quicksell)

Buyer before: http://backpack.tf/profiles/76561198055878997?time=1433833200 (June 9th)

Buyer After: http://backpack.tf/profiles/76561198055878997?time=1434178800 (June 13th)

• Mini for knife (at time of trade)

  Buyer pays ~$26

  Seller receives ~$22.60

  Scm key price ~$2.50

  26/2.50 = 10 keys

  22.60/2.50 = 9 keys

Sale 3

Sold/offered with specialized botkiller scattergun and painted black fedora for smoking frenchman's beret and 4 refined

mini on Botkiller Scattergun

lowest classified: 1.1 keys

lowest available on SCM: $3.33 USD - 15 % = $2.90 = 25 ref = 1.3 keys

(1.1-1.3) = 1.2 keys

prancers = 15 (beret) - 1.2 - 1.1 = 14 keys

Seller before: http://backpack.tf/profiles/76561198202954884?time=1434178800 (June 13th)

Seller after: http://backpack.tf/profiles/76561198202954884?time=1434265200 (June 14th)

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Sellers:

http://www.tf2outpost.com/trade/26315928 - 12 keys

http://i.imgur.com/RR3Owmp.png - 13 keys

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well, it took me some time to do it, but i had the help of Teeny, and Sugarcube. Feedback is well appreciated