Sale 1:

Sold for Cloud 9 YWN (22.5) + >4 keys in pure/items

No B/O’s on outpost.

Seller: https://backpack.tf/profiles/76561198061376237#!/compare/1495929600/1496016000

Buyer: https://backpack.tf/profiles/76561198046242806#!/compare/1496016000/1496275200

X = 27

Sale 2:

Sold for 22 keys

Seller: https://backpack.tf/profiles/76561198006544512#!/compare/1496534400/1496620800

Buyer: https://backpack.tf/profiles/76561198038719860#!/compare/1496534400/1496620800

X = 22

Sale 3:

Sold for either 21 or 22 keys

Seller: https://backpack.tf/profiles/76561198090956917#!/compare/1494892800/1494979200

Buyer: https://backpack.tf/profiles/76561198126590193#!/compare/1494979200/1495065600

It’s likely that the buyer turned the items into a key, then traded the key for the jefe.

X = 22

Sale 4:

Sold for Peace Sign Defiant Spartan (21)

http://i.imgur.com/uAlbOfp.png - B/O of 22

Seller: https://backpack.tf/profiles/76561198179707937#!/compare/1499385600/1499472000

Buyer: https://backpack.tf/profiles/76561198114820320#!/compare/1499212800/1499472000

X = 21

Sellers:

22 keys:

http://i.imgur.com/sxhqOm0.png - 5 days

http://www.tf2outpost.com/trade/29264850

Sales at:

21

22 (2x)

27

27 is an outlier. Excluding 27.

Going with 21-22.