Using last month.

Sales 1-4:

Sold for $28, $19.99, $19.98 & $8 on marketplace.tf

https://marketplace.tf/items/30761;5;u3007

$8 is quickbuyer price, excluding.

28/1.97 = ~14.2

19.99/1.97 = ~10.1

19.98/1.97 = ~10.1

X = 14

X = 10 (2x)

Sale 5:

Sold for 10 keys

Seller: https://backpack.tf/profiles/76561198386441509#!/compare/1524700800/1524787200

Buyer: https://backpack.tf/profiles/76561198169109536#!/compare/1524700800/1524787200

Untraceable (apart from key histories below), but bot.tf confirms: https://i.imgur.com/xQFBrPh.png

https://backpack.tf/item/6805927176

https://backpack.tf/item/6805927177

https://backpack.tf/item/6805927180

https://backpack.tf/item/6805927186

https://backpack.tf/item/6805927190

https://backpack.tf/item/6805927193

https://backpack.tf/item/6805927195

https://backpack.tf/item/6805927200

https://backpack.tf/item/6805927205

https://backpack.tf/item/6805927206

X = 10

Using last month.

Sale 6:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198337734785#!/compare/1524096000/1524182400

Buyer: https://backpack.tf/profiles/76561198193620161#!/compare/1524096000/1524182400

X = 7

Sale 7:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198044335614#!/compare/1525132800/1525219200

Buyer: https://backpack.tf/profiles/76561198338402780#!/compare/1525046400/1525305600

X = 6

Sale 8:

Bulk for Logo Modest

Seller: https://backpack.tf/profiles/76561198126985704#!/compare/1524355200/1524528000

Buyer: https://backpack.tf/profiles/76561198035620692#!/compare/1524355200/1524528000

Sellers:

20 keys:

https://i.imgur.com/LeIS8VU.png

https://backpack.tf/item/6561785737

~32.5:

http://www.tf2outpost.com/trade/28829635

Sales at:

6

7

10 (3x)

14

Sales at 6 and 7 took a while to sell, no reason to exclude them.

14 is an outlier, excluding 14.