Sale 1:

Sold for 36 keys pure (In a 15 day hold)

http://www.tf2outpost.com/trade/27852748 - B/O of 33, ignoring because pure sale

Seller: http://backpack.tf/profiles/76561198092700900/#!/compare/1455523200/1459728000

Buyer: http://backpack.tf/profiles/76561198210556787/#!/compare/1458111600/1459728000

X = 36

Sale 2:

Sold for Disco Beat Down Bonk Helm

http://www.tf2outpost.com/trade/27852434 - B/O of 30?

Seller: http://backpack.tf/profiles/76561198115062041/#!/compare/1455436800/1455523200

Buyer: http://backpack.tf/profiles/76561198107839402/#!/compare/1455350400/1455436800

X = 32

Sale 3:

Sold with ~2 keys in items for Pro. KS Australium Stickybomb Launcher (With 10 keys in parts)

http://www.tf2outpost.com/trade/27729393 - No B/O

Seller: http://backpack.tf/profiles/76561198097143109/#!/compare/1454486400/1456041600

Buyer: http://backpack.tf/profiles/76561198115062041/#!/compare/1454486400/1454572800

X + 2 = 27

X = 25

No current sellers

Sales at:

25

32

36 (Pure)

Calling 25 an outlier

Going with 32-36