Sale 1:

Sold for 12 keys + 16 ref (<0.5) (IDs match)

http://www.tf2outpost.com/trade/29364498 - B/O of < 12.5

Seller: https://backpack.tf/profiles/76561198045692488#!/compare/1505433600/1505520000

Buyer: https://backpack.tf/profiles/76561198075080664#!/compare/1505433600/1505520000

Even though the sale is (barely) under 12.5, I’m gonna round up as the other sales are closer to 12.5 than they are to 12, so the range will be 12-13, allowing the midpoint to represent the most common trading point.

X = 13

Sale 2:

Sold for 12 keys + 12 ref

No outpost

Seller: https://backpack.tf/profiles/76561198304138933#!/compare/1505260800/1505347200

Buyer: https://backpack.tf/profiles/76561198069559160#!/compare/1505260800/1505347200

X = 12

Sale 3:

Sold for 12 keys + 10 ref

No outpost

Seller: https://backpack.tf/profiles/76561198349886701#!/compare/1503014400/1503100800

Buyer: https://backpack.tf/profiles/76561198255530646#!/compare/1503014400/1503100800

X = 12

Sale 4:

Sold for Blizzardy Storm Panama + Strange Spec. KS Battle-scarred Airwolf Sniper Rifle (~5) + 1 key + < 0.5 keys in ref

No outpost

Seller: https://backpack.tf/profiles/76561198069559160#!/compare/1505260800/1505347200

Buyer: https://backpack.tf/profiles/76561198163558383#!/compare/1504656000/1505347200

Sale at ~5 keys worth on the non-killstreak Airwolf sniper: http://steamcommunity.com/market/listings/440/Strange%20Airwolf%20Sniper%20Rifle%20%28Battle%20Scarred%29

Without a B/O cap, this sale will be a large outlier, even without knowing what the blizzardy storm panama would be updated to.

Sale 5:

Bulk for something

Seller: https://backpack.tf/profiles/76561198075080664#!/compare/1505692800/1505952000

Buyer: https://backpack.tf/profiles/76561198085269574#!/compare/1505606400/1505692800

Sellers:

14 keys:

https://i.imgur.com/tTxPuLp.png - 1 month

Sales at:

12 (2x)

13

Going with 12-13.