Using last month

Sale 1:

Sold with a key for Voltaic Hat Protector Head Full of Hot Air (Suggestion at 10)

Seller: https://backpack.tf/profiles/76561198143320939#!/compare/1524268800/1524355200

Buyer: https://backpack.tf/profiles/76561198119621480#!/compare/1520294400/1524355200

X = 9

Sale 2:

Sold for Bubbling Magnificent Mongolian

https://i.imgur.com/k4xfmQS.png - B/O of 8

Seller: https://backpack.tf/profiles/76561198088250438#!/compare/1524528000/1524614400

Buyer: https://backpack.tf/profiles/76561198118577247#!/compare/1524268800/1524614400

Should cap

X = 8 (Capped by B/O)

Sale 3:

Sold for $15 on Marketplace.tf

https://marketplace.tf/items/30816;5;u3008

Can't find item's history

15/1.97 = ~7.61

X = 7.5

Sale 4:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198386441509#!/compare/1524268800/1524355200

Buyer: https://backpack.tf/profiles/76561198143320939#!/compare/1524268800/1524355200

X = 6

Sale 5:

Sold for Silver Cyclone Killer Solo

Seller: https://backpack.tf/profiles/76561198128012200#!/compare/1524268800/1524441600

Buyer: https://backpack.tf/profiles/76561198141152637#!/compare/1524268800/1524355200

Last time I loked into the Killer Solo, sales were all over the place. Might be better to use on the Solo.

Voltaic Head:

https://backpack.tf/suggestion/5ae1d254cf6c75066f147171

Sellers:

11 keys:

https://i.imgur.com/3X4mlgp.png

https://backpack.tf/item/6788191967

15 keys:

https://i.imgur.com/VtZF1We.png

https://backpack.tf/item/5192044739

https://i.imgur.com/TAd27rU.png (One listed for 16, doubt they'd decline 15 on that particular taunt)

https://backpack.tf/item/6647768704

https://backpack.tf/item/5185214192

25 keys:

https://i.imgur.com/DA7NsVR.png

https://backpack.tf/item/5184879778

https://backpack.tf/item/5217851404

SCM: (Taking keys as $2.47)

https://i.imgur.com/b7Uk6GA.png (Only the first 5 matter here)

$19.86 (~8.04 keys)

$19.87 (~8.04 keys)

$22.50 (~9.11 keys)

$23 (~9.31 keys)

$23.60 (~9.55 keys)

Sales at:

6

7.5

8

9

6 looks pretty low compared to the other sales, and SCM buyers are near 7 keys worth: https://i.imgur.com/b7Uk6GA.png

Excluding 6.

Going with 7.5-9.