Sale 1:

Sold for 8 keys + >0.5 keys in ref/cosmetics

http://www.tf2outpost.com/trade/28903358 - B/O of 9, re-listed several times:

http://www.tf2outpost.com/trade/28869648 - B/O of 10

http://www.tf2outpost.com/trade/28858278 - B/O of 10.3

Seller: https://backpack.tf/profiles/76561198114729364#!/compare/1493596800/1493683200

Buyer: https://backpack.tf/profiles/76561197997339757#!/compare/1493510400/1493683200

X = 9

Sale 2:

Sold for 8 keys + >0.5 keys in metal

http://www.tf2outpost.com/trade/28957228 - Deleted B/O, couldn’t get anything cached

Seller: https://backpack.tf/profiles/76561197997339757#!/compare/1493683200/1494115200

Buyer: https://backpack.tf/profiles/76561198191118333#!/compare/1493942400/1494115200

X = 9

Sale 3:

Bulk for keys

Seller: https://backpack.tf/profiles/76561198080559842#!/compare/1497225600/1497398400

Buyer: https://backpack.tf/profiles/76561198211445756#!/compare/1496966400/1497398400

Sale 4:

Sold with 1 key + 15 ref for Blizzardy Stuntman

Seller: https://backpack.tf/profiles/76561198167492863#!/compare/1499472000/1499558400

Buyer: https://backpack.tf/profiles/76561198296168912#!/compare/1499472000/1499558400

Should be used on the Stuntman.

Sale 5:

Sold for 7 keys

No outpost

Seller: https://backpack.tf/profiles/76561198058248287#!/compare/1499558400/1500336000

Buyer: https://backpack.tf/profiles/76561198167492863#!/compare/1499472000/1499558400

X = 7

Sale 6:

Bulk for Unusual shotgun

Seller: https://backpack.tf/profiles/76561198090501778#!/compare/1499644800/1499817600

Buyer: https://backpack.tf/profiles/76561198216561389#!/compare/1499731200/1499817600

Sellers:

11 keys:

http://i.imgur.com/Jl9a8uR.png - 15 days

http://i.imgur.com/ABjjDy5.png - 2 months

Sales at:

7

9 (2x)

7 is an outlier. Excluding 7.

Going with 9 flat.