Using last month.

Sales 1-3:

Sold for $18.50, $20.44, and $11.05 on marketplace.tf

https://marketplace.tf/items/30615;5;u3001

http://manic.tf/keyprice/?at=2018-08-25 - $11.05 / $1.9 = 5.82 keys

http://manic.tf/keyprice/?at=2018-08-28 - $20.44 / $1.88 = 10.87 keys

http://manic.tf/keyprice/?at=2018-09-08 - $18.50 / $1.88 = 9.84 keys

https://backpack.tf/item/4441146167 - no B/O (25th & 28th aug)

X = 11

X = 10

X = 6

Sale :

Sold for 9 keys + ~0.5 keys in metal

Seller: https://backpack.tf/profiles/76561197999225116#!/compare/1537315200/1537401600

Buyer: https://backpack.tf/profiles/76561198334946156#!/compare/1537315200/1537401600

https://backpack.tf/item/4162927189

X = 9.5

Sale :

Sold for Mega Strike Russian Arms Race (Suggestion at 5.5) + ~4 keys in items

No B/O

Seller: https://backpack.tf/profiles/76561198085935298#!/compare/1534723200/1534896000

Buyer: https://backpack.tf/profiles/76561198129565650#!/compare/1534723200/1534896000

X = 9.5

Other Sales:

https://backpack.tf/item/6605386335 (#1-3)

https://backpack.tf/item/4441146167 (#4)

https://backpack.tf/item/4162927189 (#5)

https://backpack.tf/item/5556047206 - tf2mart/swap bots

#1

Bulk or gambled or something

https://backpack.tf/profiles/76561198410429966#!/compare/1536278400/1536364800

https://backpack.tf/profiles/76561198320615503#!/compare/1536364800/1537142400

#2

Probably gambled again

https://backpack.tf/profiles/76561198320615503#!/compare/1537142400/1537401600

https://backpack.tf/profiles/76561198356834968#!/compare/1537401600/1537488000

#3

Most likely gambled

https://backpack.tf/profiles/76561198356834968#!/compare/1537401600/1537488000

https://backpack.tf/profiles/76561198093543096#!/compare/1536969600/1537574400

#4

Untraceable

https://backpack.tf/profiles/76561198056782115#!/compare/1537056000/1537401600

https://backpack.tf/profiles/76561198334598690#!/compare/1537315200/1537401600

https://i.imgur.com/e7JuTeJ.png - labelled as 6 keys + 19.33 ref

#5

Untraceable

https://backpack.tf/profiles/76561198334946156#!/compare/1537315200/1537401600

https://backpack.tf/profiles/76561198383060639#!/compare/1537142400/1537401600

#6-8

Bot.tf states 3 sold within ~13 minutes for ~9.5 keys each. Clicking them gives two different compare links:

https://backpack.tf/profiles/76561198839307425#!/compare/1535328000/1535414400

https://backpack.tf/profiles/76561198334598690#!/compare/1535328000/1535414400

https://backpack.tf/item/3901451238

https://backpack.tf/item/3901445021

https://backpack.tf/item/4465972596

One of these went to swap.gg and the other two haven't been scanned since the sale.

Even if these sales were traceable, and correct, they wouldn't affect the range as we have a sale at 9.5 already.

Mega Strike Arms Race:

https://backpack.tf/suggestion/5ba6437ccf6c756e6b37cbd1

Sellers:

https://i.imgur.com/QcX6YBE.png

https://backpack.tf/item/4441146167 - ~9.48 keys

https://backpack.tf/item/4640728341 - 10 keys

https://backpack.tf/item/4448529956 - 13 keys

Sales at:

6

9.5 (2x)

10

11

6 is low given the buyers. Excluding 6.

Going to exclude 11, given the sellers at 9.5 and 10.

Going with 9.5 flat.