Using last month.

Sale 1:

Sold for Cyclone Bunnyhopper (9.5)

No outpost

Seller: https://backpack.tf/profiles/76561198328832968#!/compare/1526169600/1526342400

Buyer: https://backpack.tf/profiles/76561198818171767#!/compare/1526169600/1526342400

X = 9.5

Sale 2:

Sold for Mega Strike Buy a Life (7.5)

No outpost

Seller: https://backpack.tf/profiles/76561198051198908#!/compare/1525996800/1526083200

Buyer: https://backpack.tf/profiles/76561198328832968#!/compare/1525996800/1526083200

X = 7.5

Sale 3:

Sold with taunt (~0.5) for Killstreak Aus Axtinguisher (~7)

No outpost

Seller: https://backpack.tf/profiles/76561198220194229#!/compare/1525564800/1525651200

Buyer: https://backpack.tf/profiles/76561198354891760#!/compare/1525478400/1525564800

X = 6.5

Sale 4:

Sold for 5 keys + Dragon slayer skin (~1)

Seller: https://backpack.tf/profiles/76561198044335614#!/compare/1525478400/1525564800

Buyer: https://backpack.tf/profiles/76561198228227148#!/compare/1525478400/1525564800

X = 6

Sale 5:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198098839154#!/compare/1525910400/1525996800

Buyer: https://backpack.tf/profiles/76561198051198908#!/compare/1525910400/1525996800

X = 5

Sale 6:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198386441509#!/compare/1525651200/1525737600

Buyer: https://backpack.tf/profiles/76561198179507871#!/compare/1525651200/1525737600

Bot.tf confirms: https://i.imgur.com/yhbJjmB.png

X = 5

Sale 7:

Sold for 5 keys (ID’s match)

Seller: https://backpack.tf/profiles/76561198079578383#!/compare/1527552000/1527724800

Buyer: https://backpack.tf/profiles/76561198114014247#!/compare/1513814400/1527638400

X = 5

Sale 8:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198089602477#!/compare/1525478400/1525564800

Buyer: https://backpack.tf/profiles/76561198220194229#!/compare/1525392000/1525564800

X = 5

Sale 9:

Sold for 4 keys + 27 ref

Seller: https://backpack.tf/profiles/76561198345507207#!/compare/1525989600/1526076000

https://backpack.tf/item/3248423085 - Buyer is untraceable

X = 5

Sale 10:

Sold with 8 ref for 5 keys

Seller: https://backpack.tf/profiles/76561198228227148#!/compare/1525564800/1525824000

Buyer: https://backpack.tf/profiles/76561198410145031#!/compare/1525737600/1525824000

X = 4.5

Sale 11:

Sold for 4 keys to a bot

Seller: https://backpack.tf/profiles/76561198148733839#!/compare/1527465600/1527552000

Buyer: https://backpack.tf/profiles/76561198386441509#!/compare/1527465600/1527552000

Bot.tf confirms: https://i.imgur.com/yhbJjmB.png

X = 4

Sale 12:

Sold for Strange Spec. KS Festive Ambassador (4)

Seller: https://backpack.tf/profiles/76561198273422715#!/compare/1525392000/1525564800

Buyer: https://backpack.tf/profiles/76561198089602477#!/compare/1525305600/1525478400

X = 4

Sale 13:

Sold for $8.25 on marketplace.tf

https://marketplace.tf/items/1109;5;u3004

Would’ve gone to a buy order.

8.25/1.96 = ~4.21

X = 4

Sale 14:

Sold for Strange Pro. KS Direct Hit (~3.5)

Seller: https://backpack.tf/profiles/76561198179507871#!/compare/1527206400/1527292800

Buyer: https://backpack.tf/profiles/76561198026129220#!/compare/1527206400/1527292800

X = 3.5

Sale 15:

Bulk for unusual black box

Seller: https://backpack.tf/profiles/76561198071687453#!/compare/1526860800/1526947200

Buyer: https://backpack.tf/profiles/76561198063640894#!/compare/1526860800/1526947200

Sale 16:

Bulk for Voltaic Captain Spacemann

Seller: https://backpack.tf/profiles/76561198060455745#!/compare/1527292800/1527379200

Buyer: https://backpack.tf/profiles/76561198164036774#!/compare/1527292800/1527379200

Sale 17:

Bulk for Burning Fly Guy

Seller: https://backpack.tf/profiles/76561198164036774#!/compare/1527465600/1527552000

Buyer: https://backpack.tf/profiles/76561198079578383#!/compare/1527465600/1527552000

Sellers:

5 keys:

https://i.imgur.com/tJQ3IyM.png

https://backpack.tf/item/4363110367

~5.6 keys:

https://i.imgur.com/JHkM9sj.png

https://backpack.tf/item/2706918277

9 keys:

https://i.imgur.com/Cmu02xq.png

https://backpack.tf/item/2774522474

https://backpack.tf/item/4553986908

14 keys:

https://i.imgur.com/POdJL5W.png

https://backpack.tf/item/3820900987

Sales at:

3.5

4 (3x)

4.5

5 (5x)

6

6.5

7.5

9.5

Excluding anything at or higher than 6 given the unsolds for significantly cheaper.

3.5 seems low, excluding.

Going with 4-5.