Sale 1: Not using

Probably sold for paypal

http://www.tf2outpost.com/trade/26929918

http://backpack.tf/profiles/76561198072278717?time=1443855600&compare=1444201200 (Seller)

http://backpack.tf/profiles/76561198049370335?time=1444028400&compare=1443942000 (Buyer)

Sale 2: Not using

Sold probably for keys, not sure how many

http://www.tf2outpost.com/trade/27187694

http://backpack.tf/profiles/76561198049370335?time=1444806000&compare=1444892400 (Seller)

http://backpack.tf/profiles/76561198073438708?time=1444892400&compare=1444806000 (Buyer)

May have sold for 18. Even then, it looks like an outlier, compared to other sales.

Sale 3:

Sold with Bubbling Veil for Ghastly Ghosts Jr. Tyrant's Helm

http://www.tf2outpost.com/trade/27387688

http://www.tf2outpost.com/trade/27277088 <-- Offered here

http://backpack.tf/profiles/76561198068090261?time=1446883200&compare=1446969600 (Seller)

http://backpack.tf/profiles/76561198035884807?time=1446796800&compare=1446969600 (Buyer)

X + 38 = 68

X = 30

Sale 4:

Sold for:

Duped Stormy Storm Le Party Phantom

Orbiting Fire Whirly Warrior

http://www.tf2outpost.com/trade/27400821

http://backpack.tf/profiles/76561198035884807?time=1448092800&compare=1448179200 (Seller)

http://backpack.tf/profiles/76561198026225027?time=1448179200&compare=1446883200 (Buyer)

Capped by B/O (35)

X = (20 + ?)0.9

X = 18 + (?*0.9)

Whirly Warrior Mini:

Sold immediately for 20 (which can be seen in the seller's link in the sale above)

http://www.tf2outpost.com/trade/27474199

http://backpack.tf/profiles/76561198035884807?time=1448092800&compare=1448179200

No mini for Party Phantom needed (capped by B/O). I doubt that a duped Le Party Phantom would be worth 19 keys.

Sales at:

30

35

30-35