Using last month

Sale 1:

Bot.tf sale at 7 keys + 14 ref

https://i.imgur.com/4EMVIq4.png

https://i.imgur.com/ZVMJggh.png (cached)

https://backpack.tf/profiles/76561198344933095#!/compare/1524355200/1524441600

https://backpack.tf/item/6573136591 - Buyer can’t yet be identified

X = 7.5

Sale 2:

Sold for 5 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1524182400/1524268800

Buyer: https://backpack.tf/profiles/76561198089467641#!/compare/1524182400/1524268800

X = 5.5

Sale 3:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198259342040#!/compare/1523404800/1523491200

Buyer: https://backpack.tf/profiles/76561198160416963#!/compare/1523491200/1523577600

X = 5

Sale 4:

Sold for 4 keys

Seller: https://backpack.tf/profiles/76561198155558267#!/compare/1524268800/1524355200

Buyer: https://backpack.tf/profiles/76561198172198154#!/compare/1524268800/1524355200

X = 4

Sale 5:

Sold for 4 keys

Seller: https://backpack.tf/profiles/76561198172198154#!/compare/1524268800/1524355200

Buyer: https://backpack.tf/profiles/76561198120768380#!/compare/1524268800/1524355200

X = 4

Sale 6:

Bulk for pure

Seller: https://backpack.tf/profiles/76561198068408798#!/compare/1524182400/1524268800

Buyer: https://backpack.tf/profiles/76561198155558267#!/compare/1524182400/1524268800

Sellers:

~5.73 keys:

https://i.imgur.com/Q8rtFBD.png

https://backpack.tf/item/4451965325

8 keys:

https://i.imgur.com/pt8Yl4q.png

https://backpack.tf/item/3767948016

14 keys:

https://i.imgur.com/6o5Ks7I.png

https://backpack.tf/item/4231961157

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

https://backpack.tf/item/6297214704

17 keys:

http://www.tf2outpost.com/trade/29622038

18 keys:

https://i.imgur.com/9ECr3di.png

https://backpack.tf/item/3820364294

Offers:

http://www.tf2outpost.com/trade/29627195

Sales at:

4 (2x)

5

5.5

7.5

https://i.imgur.com/59rPPjx.png - Buyer at ~5.36 keys, excluding 4 and 5.

Going with 5.5-7.5