Using last month.

Sale 1:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198050726553#!/compare/1538092800/1538179200

Buyer: https://backpack.tf/profiles/76561198827413603#!/compare/1538092800/1538179200

https://backpack.tf/item/3557195020

X = 7

Sales 2 & 3:

Sold for $11.45 & $8.99 on marketplace.tf

https://marketplace.tf/items/1114;5;u3003

https://manic.tf/keyprice/?at=2018-10-02 - $8.99 / $1.8 = 4.99 keys

https://manic.tf/keyprice/?at=2018-10-03 - $11.45 / $1.8 = 6.36 keys

X = 6.5

X = 5

Sale 4:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198030343929#!/compare/1539216000/1539302400

Buyer: https://backpack.tf/profiles/76561198148511293#!/compare/1539129600/1539302400

https://backpack.tf/item/6645774623

X = 6

Sale 5:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198363395191#!/compare/1539043200/1539129600

Buyer: https://backpack.tf/profiles/76561198148511293#!/compare/1539043200/1539129600

https://backpack.tf/item/4379564034

X = 5

Sale 6:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198841174439#!/compare/1537833600/1538006400

Buyer: https://backpack.tf/profiles/76561198148511293#!/compare/1537920000/1538006400

https://backpack.tf/item/3557195020

X = 5

Sale 7:

Sold for ~4 keys in items

Seller: https://backpack.tf/profiles/76561198236692896#!/compare/1537401600/1539561600

Buyer: https://backpack.tf/profiles/76561198212369645#!/compare/1537488000/1537574400

https://backpack.tf/item/4660111309

X = 4

Other Sales:

https://backpack.tf/item/6880834713 (#1)

https://backpack.tf/item/6645774623 (#2)

https://backpack.tf/item/4970485581 (#3)

https://backpack.tf/item/4660111309 (#4)

https://backpack.tf/item/4379564034 (#5 & #6)

https://backpack.tf/item/3568163732 (#7 & #8)

https://backpack.tf/item/3557195020 (#9-11)

https://backpack.tf/item/2696644226 (#12)

https://backpack.tf/item/2691269563 (#13)

https://backpack.tf/item/4429623037 - not unusual at the time

#1

hot case

https://backpack.tf/profiles/76561198431620499#!/compare/1537315200/1539561600

https://backpack.tf/profiles/76561198070126019#!/compare/1536969600/1537315200

#2

Untraceable

https://backpack.tf/profiles/76561198153789411#!/compare/1538611200/1538697600

https://backpack.tf/profiles/76561198030343929#!/compare/1539043200/1539216000

#3

Untraceable purchase from a bot, then Bulk for Burning Trucker’s Topper

https://backpack.tf/profiles/76561198148511293#!/compare/1537228800/1537315200

https://backpack.tf/profiles/76561198271058415#!/compare/1536451200/1537315200

https://backpack.tf/profiles/76561198385940902#!/compare/1537308000/1537394400

https://i.imgur.com/2uFX0mD.png - Labelled as 6 keys on bot.tf

Seller show up in the history because they re-sold before the item was scanned.

This item was gambled all throughout its history after this trade.

#4

SCM

https://backpack.tf/profiles/76561198212369645#!/compare/1538352000/1538438400

https://backpack.tf/profiles/76561198113899098#!/compare/1538352000/1538438400

#5

Untraceable

https://backpack.tf/profiles/76561198133672650#!/compare/1538870400/1539043200

https://backpack.tf/profiles/76561198363395191#!/compare/1538956800/1539043200

#6

Sold to an unboxer for an Aus Knife

https://backpack.tf/profiles/76561198148511293#!/compare/1539129600/1539302400

https://backpack.tf/profiles/76561198302374673#!/compare/1539216000/1539302400

#7

SCM

https://backpack.tf/profiles/76561198059738981#!/compare/1537574400/1537660800

https://backpack.tf/profiles/76561198123097015#!/compare/1537574400/1537660800

#8

Bulk for something

https://backpack.tf/profiles/76561198123097015#!/compare/1538870400/1538956800

https://backpack.tf/profiles/76561197997268820#!/compare/1538697600/1538956800

Was later dumped on scrap, which shouldn’t be used here.

#9

Bulk for DBD Boxcar

https://backpack.tf/profiles/76561198148511293#!/compare/1538006400/1538092800

https://backpack.tf/profiles/76561198356483977#!/compare/1537920000/1538092800

#10

Bulk for Tesla Coil Airdog

https://backpack.tf/profiles/76561198356483977#!/compare/1537920000/1538092800

https://backpack.tf/profiles/76561198050726553#!/compare/1538006400/1538092800

#11

Untraceable

https://backpack.tf/profiles/76561198827413603#!/compare/1538265600/1538352000

https://backpack.tf/profiles/76561198243277432#!/compare/1536796800/1539302400

#12

Sold for Smoking Merc’s Mohawk

https://backpack.tf/profiles/76561198169728837#!/compare/1538870400/1539043200

https://backpack.tf/profiles/76561197992998498#!/compare/1538784000/1539216000

#13

Untraceable

https://backpack.tf/profiles/76561198093501381#!/compare/1537056000/1537142400

https://backpack.tf/profiles/76561198374038715#!/compare/1537056000/1537142400

Sellers:

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

https://backpack.tf/item/4660111309 - 7 keys

https://backpack.tf/item/2705955042 - 8 keys

https://backpack.tf/item/4065527713 - 10 keys

https://backpack.tf/item/4970485581 - 10 keys

https://backpack.tf/item/2886435854 - 10 keys

Sales at:

5 (3x)

6

6.5

7

Going with 5-7.