Using sales that were less than a month old when I started making this suggestion (26/9)

Sales 1-5:

Sold for $14.99, $13.50, $10.99, $9, & $6.17 on marketplace.tf

https://marketplace.tf/items/1119;5;u3006

http://manic.tf/keyprice/?at=2018-08-28 - $14.99 / $1.88 = 7.97 keys

http://manic.tf/keyprice/?at=2018-09-01 - $13.50 / $1.88 = 7.18 keys

http://manic.tf/keyprice/?at=2018-10-01 - $10.99 / $1.83 = 6.01 keys

http://manic.tf/keyprice/?at=2018-09-10 - $9 / $1.87 = 4.81 keys

http://manic.tf/keyprice/?at=2018-09-22 - $6.17 / $1.84 = 3.35 keys

Can’t find any of the histories.

X = 8

X = 7

X = 6

X = 5

X = 3.5

Other Sales:

https://backpack.tf/item/2809219386 (#1)

https://backpack.tf/item/6003765419 - tf2mart

https://backpack.tf/item/4471564862 - marketplace

https://backpack.tf/item/4908148839 - scammed

#1

Untraceable

https://backpack.tf/profiles/76561198334598690#!/compare/1536789600/1536876000

https://backpack.tf/item/2809219386 - buyer hasn’t been scanned

#2

SCM

https://backpack.tf/profiles/76561198848985609#!/compare/1537833600/1537920000

https://backpack.tf/profiles/76561198073386321#!/compare/1538179200/1538352000

Sales at:

3.5

5

6

7

8

3.5 is an outlier, given current buyers. Excluding 3.5.

Going with 5-8.