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

Sales 1-3:

Sold for $19.50, $21.95, & $22.98 on marketplace.tf

https://marketplace.tf/items/30921;5;u3006

https://backpack.tf/item/7093334738 - no B/O

https://backpack.tf/item/6709879461 ($21.95 sale)

http://www.tf2outpost.com/trade/29746955 - B/O of 10

http://manic.tf/keyprice/?at=2018-09-24 - $19.5 / $1.84 = 10.60 keys

http://manic.tf/keyprice/?at=2018-09-25 - $21.95 / $1.83 = 11.99 keys

http://manic.tf/keyprice/?at=2018-10-02 - $22.98 / $1.8 = 12.77 keys

X = 13

X = 12

X = 11

Other Sales:

https://backpack.tf/item/7088377633 (#1)

https://backpack.tf/item/6934681176 (#2)

https://backpack.tf/item/6648234394 (#3)

https://backpack.tf/item/6551701793 (#4 & 5)

https://backpack.tf/item/6684526120 (#6)

https://backpack.tf/item/6501134659 (#7-9)

https://backpack.tf/item/6684526120 - marketplace

#1

SCM

https://backpack.tf/profiles/76561198057358637#!/compare/1536710400/1536796800

https://backpack.tf/profiles/76561198344749907#!/compare/1536364800/1537488000

#2

Bot.tf purchase from a scammer

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

https://backpack.tf/item/6934681176

#3

Untraceable

https://backpack.tf/profiles/76561198030588700#!/compare/1537142400/1537401600

https://backpack.tf/profiles/76561198044684270#!/compare/1537228800/1537315200

#4

Bulk for Abduction Phononaut

https://backpack.tf/profiles/76561198121171912#!/compare/1535587200/1535932800

https://backpack.tf/profiles/76561198114764948#!/compare/1535760000/1535932800

#5

Bulk for Darkblaze Crocleather Slouch

https://backpack.tf/profiles/76561198114764948#!/compare/1535932800/1536192000

https://backpack.tf/profiles/76561198091502579#!/compare/1536105600/1536192000

#6

Untraceable, labelled at 8 keys and 6 ref on bot.tf

https://backpack.tf/profiles/76561198129984735#!/compare/1538956800/1539043200

https://backpack.tf/profiles/76561198312583107#!/compare/1538956800/1539043200

https://i.imgur.com/rj3umD3.png

#7

Bulk for pure

https://backpack.tf/profiles/76561198352969437#!/compare/1538006400/1538179200

https://backpack.tf/profiles/76561198054201896#!/compare/1538092800/1538179200

#8

Bulk for pure

https://backpack.tf/profiles/76561198054201896#!/compare/1538092800/1538179200

https://backpack.tf/profiles/76561198087448314#!/compare/1538092800/1538179200

#9

bot.tf purchase from a trade-banned account

https://backpack.tf/item/6501134659

https://i.imgur.com/rj3umD3.png - labelled as 8 keys + 6 ref

Sellers:

https://i.imgur.com/zfLML5s.png

https://i.imgur.com/dRexK15.png

https://backpack.tf/item/6684526120 - ~10.77 keys

https://backpack.tf/item/6934681176 - 11 keys

https://backpack.tf/item/6551701793 - 11 keys

https://backpack.tf/item/6501134659 - 14 keys

https://backpack.tf/item/6573295163 - 18 keys

https://backpack.tf/item/6562424424 - 20 keys

Sales at:

11

12

13

https://i.imgur.com/AXnHM10.png

At the time I started working on the suggestion, sellers were as low as 14 keys. Given the amount they have dropped by, it may be a good idea to leave this open and see how the cheaper sellers go.

Going with 11-13 for now.

https://backpack.tf/profiles/76561198335791307#!/compare/1540425600/1540512000

https://backpack.tf/profiles/76561198090822133#!/compare/1540425600/1540512000

https://backpack.tf/item/6934681176

https://i.imgur.com/cP6oPWJ.png

sold for cyclone conga (11) with a b/o of ~10.75

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

https://backpack.tf/item/6934681176

https://backpack.tf/item/6501134659

https://backpack.tf/item/6684526120

https://backpack.tf/item/6562424424

https://backpack.tf/item/6573295163

sellers now ranging from 10.5-11 (and another at 18). don't know what to do with this.