Using last month.

Sale 1:

https://marketplace.tf/items/1112;5;u3001

http://manic.tf/keyprice/?at=2018-08-23 - $10.99 / $1.9 = 5.78 keys

Couldn’t find the item’s history.

X = 6

Sale 2:

Sold for 5 keys + ~0.5 keys in metal

Seller: https://backpack.tf/profiles/76561198334598690#!/compare/1535155200/1535241600

Buyer: https://backpack.tf/profiles/76561198067663328#!/compare/1535155200/1535241600

https://backpack.tf/item/6504118252

https://i.imgur.com/YCSsq9L.png

X = 5.5

Sale 3:

Sold for 5 keys + ~0.5 keys in metal

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1534723200/1534809600

Buyer: https://backpack.tf/profiles/76561198199217834#!/compare/1534809600/1534896000

https://backpack.tf/item/2808265960

X = 5.5

Sale 4:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198075368942#!/compare/1536451200/1536710400

Buyer: https://backpack.tf/profiles/76561198066345235#!/compare/1536451200/1536710400

https://backpack.tf/item/4501284447

X = 5

Sale 5:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198208162248#!/compare/1536364800/1536451200

Buyer: https://backpack.tf/profiles/76561198301172421#!/compare/1534896000/1536451200

https://backpack.tf/item/2689840977

X = 5

Sale 6:

Sold to a quickbuyer for 4 keys + ~0.5 keys in metal

Seller: https://backpack.tf/profiles/76561198244253680#!/compare/1535500800/1535587200

Buyer: https://backpack.tf/profiles/76561198044684270#!/compare/1535587200/1537401600

https://backpack.tf/item/6504118252

X = 4.5

Sale 7:

Sold to a bot for 4 keys + ~0.5 keys in metal (Buyer’s end)

Seller: https://backpack.tf/profiles/76561198158964214#!/compare/1535241600/1535760000

Buyer: https://backpack.tf/profiles/76561198334598690#!/compare/1535673600/1535760000

https://backpack.tf/item/3515469084

https://i.imgur.com/YCSsq9L.png

X = 4.5

Other Sales:

https://backpack.tf/item/6504118252 (#1)

https://backpack.tf/item/4501284447 (#2, rest weren’t unusual at the time)

https://backpack.tf/item/2689840977 (#3 & #4)

https://backpack.tf/item/7114015421 - marketplace.tf

https://backpack.tf/item/6734713890 - tradeit.gg/scammed

#1

Sold for Steaming Glengarry Bonnet + ~2 keys in pure/items

https://backpack.tf/profiles/76561198067663328#!/compare/1535155200/1535241600

https://backpack.tf/profiles/76561198244253680#!/compare/1535241600/1535328000

Way too high. No B/O here.

#2

Untraceable

https://backpack.tf/profiles/76561198066345235#!/compare/1536796800/1536883200

https://backpack.tf/profiles/76561198137988566#!/compare/1536710400/1536883200

#3

Untraceable

https://backpack.tf/profiles/76561198301172421#!/compare/1536451200/1537488000

https://backpack.tf/profiles/76561198124728984#!/compare/1536969600/1537056000

#4

Untraceable

https://backpack.tf/profiles/76561198124728984#!/compare/1536969600/1537056000

https://backpack.tf/profiles/76561197994783413#!/compare/1536969600/1537056000

Sellers:

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

https://backpack.tf/item/3515469084 - 7 keys

Sales at:

4.5 (2x)

5 (2x)

5.5 (2x)

6

Going with 4.5-6.