Using last 2 months due to abundance of sales here.

Sales 1-7

Sold for $14.30, $25.90, $25.49, $17.20, $17.99, $25, and $25.89 on marketplace.tf

https://marketplace.tf/items/30662;5;u96

https://backpack.tf/item/6975491217 - No B/O on outpost

https://backpack.tf/item/6729826337 - No outpost

Couldn’t find the other 5 histories.

http://manic.tf/keyprice/?at=2018-07-02 - $14.3 / $1.97 = 7.26 keys

http://manic.tf/keyprice/?at=2018-07-04 - $25.9 / $1.98 = 13.08 keys

http://manic.tf/keyprice/?at=2018-07-11 - $25.49 / $1.97 = 12.94 keys

http://manic.tf/keyprice/?at=2018-07-13 - $17.2 / $1.97 = 8.73 keys

http://manic.tf/keyprice/?at=2018-08-04 - $17.99 / $1.89 = 9.52 keys

http://manic.tf/keyprice/?at=2018-08-08 - $25 / $1.89 = 13.23 keys

http://manic.tf/keyprice/?at=2018-08-15 - $25.89 / $1.88 = 13.77 keys

X = 14

X = 13 (3x)

X = 9.5

X = 8.5

X = 7.5

Sale 8:

Sold for Strange Pro. KS Wrench (~7.5) + Banjo (~1.25) + 1 key

No outpost

Seller: https://backpack.tf/profiles/76561198122057139#!/compare/1533513600/1533600000

Buyer: https://backpack.tf/profiles/76561198061666453#!/compare/1532822400/1533600000

https://backpack.tf/item/6947768167

X = 10

Sale 9:

Sold for 10 keys

Seller: https://backpack.tf/profiles/76561198832602199#!/compare/1534982400/1535068800

Buyer: https://backpack.tf/profiles/76561198390577416#!/compare/1535068800/1535155200

https://backpack.tf/item/6947768167

X = 10

Sale 10:

Sold with cheap skins for 9 keys

Seller: https://backpack.tf/profiles/76561198346669763#!/compare/1534982400/1535068800

Buyer: https://backpack.tf/profiles/76561198137828769#!/compare/1534982400/1535068800

https://backpack.tf/item/5672905508

X = 9

Sale 11:

Sold to a quickbuyer for 8 keys + 10 ref

Seller: https://backpack.tf/profiles/76561198390577416#!/compare/1535155200/1535241600

Buyer: https://backpack.tf/profiles/76561198061275415#!/compare/1535155200/1535241600

https://backpack.tf/item/6947768167

X = 8.5

Sale 12:

Quicksold for 8 keys

Seller: https://backpack.tf/profiles/76561198269484722#!/compare/1532304000/1532390400

Buyer: https://backpack.tf/profiles/76561198302044876#!/compare/1532304000/1532390400

https://backpack.tf/item/6975491217

X = 8

Sale 13:

Sold for 8 keys + 4 ref

Seller: https://backpack.tf/profiles/76561198302044876#!/compare/1532649600/1532736000

Buyer: https://backpack.tf/profiles/76561198079631972#!/compare/1532649600/1532736000

https://backpack.tf/item/6975491217

X = 8

Sale 14:

Quicksold for 8 keys + 2 ref

Seller: https://backpack.tf/profiles/76561198069493147#!/compare/1532736000/1532822400

Buyer: https://backpack.tf/profiles/76561198139389402#!/compare/1532736000/1532822400

https://backpack.tf/item/6947768167

X = 8

Sale 15:

Sold for 8 keys

Seller: https://backpack.tf/profiles/76561198092970200#!/compare/1534982400/1535068800

Buyer: https://backpack.tf/profiles/76561198346669763#!/compare/1534809600/1534982400

https://backpack.tf/item/5672905508

X = 8

Sale 16:

Bought from scrap.tf for 7 keys + ~0.5 keys in metal

Seller: https://backpack.tf/profiles/76561198135388328#!/compare/1530748800/1530835200

Buyer: https://backpack.tf/profiles/76561198219288407#!/compare/1530748800/1530835200

https://backpack.tf/item/4236312480

X = 7.5

Sale 17:

Sold to scrap.tf for 6 keys + ~1 key in metal

Seller: https://backpack.tf/profiles/76561198086575698#!/compare/1531267200/1531440000

Buyer: https://backpack.tf/profiles/76561198135388328#!/compare/1531267200/1531353600

https://backpack.tf/item/6975491217

X = 7

Other Sales:

https://backpack.tf/item/4260254974 - All gambled/untraceable

#1

Bought from scrap.tf and dumped on tf2mart

https://backpack.tf/profiles/76561198135388328#!/compare/1531267200/1531353600

https://backpack.tf/item/6975491217

#2

Dunno, probably gambled or something

https://backpack.tf/profiles/76561198131633162#!/compare/1532217600/1532304000

https://backpack.tf/profiles/76561198085481962#!/compare/1531958400/1532304000

https://backpack.tf/item/6975491217

#3

Untraceable

https://backpack.tf/profiles/76561198085481962#!/compare/1531958400/1532304000

https://backpack.tf/profiles/76561198269484722#!/compare/1532217600/1532304000

https://backpack.tf/item/6975491217

#4

Untraceable

https://backpack.tf/profiles/76561198054088592#!/compare/1534118400/1534291200

https://backpack.tf/profiles/76561198056745114#!/compare/1533772800/1534291200

https://backpack.tf/item/6975491217

#5

Untraceable, dumped on scrap.tf

https://backpack.tf/profiles/76561198255411360#!/compare/1532736000/1532822400

https://backpack.tf/profiles/76561198135388328#!/compare/1532736000/1532822400

https://backpack.tf/item/6947768167

#6

Untraceable, bought from scrap.tf

https://backpack.tf/profiles/76561198135388328#!/compare/1532736000/1532822400

https://backpack.tf/profiles/76561198069493147#!/compare/1532736000/1532822400

https://backpack.tf/item/6947768167

#7

Untraceable

https://backpack.tf/profiles/76561198139389402#!/compare/1532822400/1532908800

https://backpack.tf/profiles/76561198160198066#!/compare/1532822400/1533254400

https://backpack.tf/item/6947768167

#8

Untraceable

https://backpack.tf/profiles/76561198160198066#!/compare/1533254400/1533513600

https://backpack.tf/profiles/76561198122057139#!/compare/1533427200/1533513600

https://backpack.tf/item/6947768167

#9

Bulk

https://backpack.tf/profiles/76561198061666453#!/compare/1533600000/1534377600

https://backpack.tf/profiles/76561198169939863#!/compare/1534291200/1534377600

https://backpack.tf/item/6947768167

#10

Bulk

https://backpack.tf/profiles/76561198169939863#!/compare/1534636800/1534809600

https://backpack.tf/profiles/76561198126114757#!/compare/1534723200/1534809600

https://backpack.tf/item/6947768167

#11

Untraceable, buyer’s backpack only recently scanned for the first time

https://backpack.tf/profiles/76561198820044573#!/compare/1532044800/1532131200

https://backpack.tf/item/6784257649

#12

Untraceable

https://backpack.tf/profiles/76561198054758757#!/compare/1531008000/1531094400

https://backpack.tf/profiles/76561198363721779#!/compare/1531008000/1531180800

https://backpack.tf/item/6687708793

#13

Untraceable

https://backpack.tf/profiles/76561198363721779#!/compare/1531180800/1531267200

https://backpack.tf/profiles/76561198123631904#!/compare/1531180800/1531267200

https://backpack.tf/item/6687708793

#14

Untraceable, probably gambled

https://backpack.tf/profiles/76561198123631904#!/compare/1531180800/1531267200

https://backpack.tf/profiles/76561198092449612#!/compare/1531180800/1531267200

https://backpack.tf/item/6687708793

#15

Untraceable, buyer doesn’t seem to appear

https://backpack.tf/profiles/76561198317606171#!/compare/1530316800/1530403200

https://backpack.tf/profiles/76561198289262378#!/compare/1530316800/1530403200

https://gyazo.com/58dd490f3220d65a683147e5933a46df - Labelled as 7 keys + 31 ref here

https://backpack.tf/item/5108774387

#16

Untraceable, history is probably missing someone inbetween

https://backpack.tf/profiles/76561198289262378#!/compare/1530403200/1530489600

https://backpack.tf/profiles/76561198026129220#!/compare/1530403200/1530489600

https://backpack.tf/item/5108774387

#17

Same story as #16, though it’s looking more likely that it was gambled.

https://backpack.tf/profiles/76561198026129220#!/compare/1530576000/1530662400

https://backpack.tf/profiles/76561198063383864#!/compare/1530835200/1531267200

https://backpack.tf/item/5108774387

#18

Gambled

https://backpack.tf/profiles/76561198063383864#!/compare/1530835200/1531267200

https://backpack.tf/profiles/76561198092449612#!/compare/1531180800/1531267200

https://backpack.tf/item/5108774387

#19

Gambled again

https://backpack.tf/profiles/76561198092449612#!/compare/1531180800/1531267200

https://backpack.tf/profiles/76561198197481041#!/compare/1530921600/1531267200

https://backpack.tf/item/5108774387

#20

Gambled again

https://backpack.tf/profiles/76561198074153368#!/compare/1532217600/1532304000

https://backpack.tf/profiles/76561198240537922#!/compare/1532217600/1532304000

https://backpack.tf/item/5108774387

#21

Gambled again

https://backpack.tf/profiles/76561198240537922#!/compare/1532304000/1532390400

https://backpack.tf/profiles/76561198024152496#!/compare/1532304000/1532390400

https://backpack.tf/item/5108774387

#22

Untraceable, dumped on scrap.tf

https://backpack.tf/profiles/76561198024152496#!/compare/1532390400/1532476800

https://backpack.tf/profiles/76561198135388328#!/compare/1532390400/1532476800

https://backpack.tf/item/5108774387

#23

Bought off scrap.tf for 7 keys + an untraceable amount of metal

https://backpack.tf/profiles/76561198135388328#!/compare/1532390400/1532476800

https://backpack.tf/profiles/76561198082933255#!/compare/1532390400/1532476800

https://backpack.tf/item/5108774387

#24

SCM

https://backpack.tf/profiles/76561198082933255#!/compare/1533168000/1533686400

https://backpack.tf/profiles/76561198052218255#!/compare/1533686400/1533772800

https://backpack.tf/item/5108774387

#25

Bulk for Beams Football Helmet

https://backpack.tf/profiles/76561198052218255#!/compare/1534723200/1534896000

https://backpack.tf/profiles/76561198312583107#!/compare/1534809600/1534896000

https://backpack.tf/item/5108774387

#26

Untraceable

https://backpack.tf/profiles/76561198106288924#!/compare/1534550400/1534723200

https://backpack.tf/profiles/76561198337734785#!/compare/1534636800/1534723200

https://backpack.tf/item/4470534560

#27

Untraceable, only the metal matches

https://backpack.tf/profiles/76561198337734785#!/compare/1535328000/1535414400

https://backpack.tf/profiles/76561198120481030#!/compare/1535241600/1535414400

https://backpack.tf/item/4470534560

#28

Bulk/untraceable

https://backpack.tf/profiles/76561198099260958#!/compare/1530921600/1531008000

https://backpack.tf/profiles/76561198089253101#!/compare/1530921600/1531008000

https://backpack.tf/item/4245702031

#29

Untraceable

https://backpack.tf/profiles/76561198089253101#!/compare/1531008000/1531094400

https://backpack.tf/profiles/76561198132167450#!/compare/1509667200/1531008000

https://backpack.tf/item/4245702031

#30

Untraceable, buyer was probably private or something

https://backpack.tf/profiles/76561198002757046#!/compare/1530576000/1530662400

https://backpack.tf/item/4245555388

#31

Untraceable, only 4 keys match

https://backpack.tf/profiles/76561198219288407#!/compare/1530921600/1531008000

https://backpack.tf/profiles/76561198359061595#!/compare/1531008000/1531094400

https://backpack.tf/item/4236312480

#32

Sold for Stormy Sola Topi

https://backpack.tf/profiles/76561198079631972#!/compare/1533686400/1534118400

https://backpack.tf/profiles/76561197997268820#!/compare/1533600000/1533686400

https://backpack.tf/item/6975491217

Can be used on the Sola Topi.

Sellers:

https://gyazo.com/4b910c36d39a293e1d227086f8cd7cef

https://backpack.tf/item/5108774387 - 10 keys

https://backpack.tf/item/6947768167 - ~11.97 keys

https://backpack.tf/item/4201642851 - 12 keys

https://backpack.tf/item/6975491217 - 12 keys

Sales at:

7

7.5 (2x)

8 (4x)

8.5 (2x)

9

9.5

10 (2x)

13 (3x)

14

Sales at 13-14 are definitely outliers, given the 4-month unsold at 12. Excluding 13+.

7.5-8 are pretty low, excluding.

Some sales at 8 may have quicksold, or come from scrap.tf, but they are way too common to be excluded, as supported by the sales for even lower than 8. Keeping 8 in the range.

Going with 8-10.