Using sales since august due to the lack of sales here.

Sale 1:

Sold for 8 keys

Seller: https://backpack.tf/profiles/76561198833317554#!/compare/1533859200/1533945600

Buyer: https://backpack.tf/profiles/76561198423162555#!/compare/1533945600/1534464000

https://backpack.tf/item/6252757543

https://i.imgur.com/Q0W0kXZ.png

X = 8

Sale 2:

Sold for Skill Gotten Gains Soviet Strongarm (6.5)

No outpost

Seller: https://backpack.tf/profiles/76561198060280493#!/compare/1537056000/1537142400

Buyer: https://backpack.tf/profiles/76561198268003154#!/compare/1537056000/1537142400

https://backpack.tf/item/6905416093

X = 6.5

Sale 3:

Sold to a bot for 4 keys + 2 ref

Seller: https://backpack.tf/profiles/76561198370578676#!/compare/1533340800/1533600000

Buyer: https://backpack.tf/profiles/76561198363395191#!/compare/1533513600/1533600000

https://backpack.tf/item/6527209463

X = 4

Sale 4:

Sold for $9.13 on marketplace.tf

https://marketplace.tf/items/30844;5;u3001

Would end up being around 5 keys, which is currently lower than quickbuyers.

Other Sales:

https://backpack.tf/item/7082198767 (#1)

https://backpack.tf/item/6809953081 (#2 & #3)

https://backpack.tf/item/6527209463 (#4)

https://backpack.tf/item/6252757543 (#5)

https://backpack.tf/item/6512822129 - Not unusual at the time

#1

Untraceable

https://backpack.tf/profiles/76561198290033158#!/compare/1535328000/1535414400

https://backpack.tf/profiles/76561198124190275#!/compare/1521158400/1536796800

#2

Untraceable

https://backpack.tf/profiles/76561198223191956#!/compare/1535328000/1535414400

https://backpack.tf/profiles/76561198200385228#!/compare/1535328000/1535414400

#3

SCM

https://backpack.tf/profiles/76561198223191956#!/compare/1534550400/1534896000

#4

Untraceable

https://backpack.tf/profiles/76561198031007256#!/compare/1533859200/1533945600

https://backpack.tf/profiles/76561198145045432#!/compare/1486425600/1536710400

#5

Untraceable

https://backpack.tf/profiles/76561198057034390#!/compare/1533427200/1533513600

https://backpack.tf/profiles/76561198833317554#!/compare/1533427200/1533513600

https://i.imgur.com/Q0W0kXZ.png - Labelled as 5 keys + 18 ref

Sellers:

https://i.imgur.com/QUD0tgQ.png

https://backpack.tf/item/6260021839 - 12 keys

Sales at:

4

6.5

8

4 is too low, excluding.

Going with 6.5-8.