Using last month.

The Sale:

Sold for 10 keys

Seller: https://backpack.tf/profiles/76561198249976824#!/compare/1562889600/1562976000

Buyer: https://backpack.tf/profiles/76561198113634055#!/compare/1562803200/1563235200

https://backpack.tf/item/6758211466

X = 10

Marketplace Sales:

https://marketplace.tf/items/tf2/30840;5;u3005

$15.61, Jul 12th

$18.80, Jul 15th

$18.80, Jul 17th

$15.50, Jul 30th

https://manic.tf/keyprice/?at=2019-07-12 - $15.61 / $1.83 = 8.53 keys

https://manic.tf/keyprice/?at=2019-07-15 - $18.80 / $1.83 = 10.27 keys

https://manic.tf/keyprice/?at=2019-07-17 - $18.80 / $1.82 = 10.33 keys

https://manic.tf/keyprice/?at=2019-07-30 - $15.5 / $1.8 = 8.61 keys

X = 10 (2x)

X = 8.5

Other Sales:

https://backpack.tf/item/6386255812 (#1)

https://backpack.tf/item/5794453802 (#2 & #3)

https://backpack.tf/item/6211743783 (#4 & #5)

https://backpack.tf/item/5367299346 - marketplace

https://backpack.tf/item/6181419648 - mannco

https://backpack.tf/item/5817820035 - marketplace

https://backpack.tf/item/7510005647 - bot to bot owner

https://backpack.tf/item/6990641510 - scrap/marketplace

https://backpack.tf/item/6746962507 - marketplace

https://backpack.tf/item/5504883973 - tradeit

#1

Untraceable

https://backpack.tf/profiles/76561197998850076#!/compare/1563408000/1563494400

https://backpack.tf/profiles/76561198340634356#!/compare/1563408000/1563494400

https://i.imgur.com/gYhuSFE.png - labelled as an 8 key + 4 ref purchase (~8 keys)

#2

Untraceable

https://backpack.tf/profiles/76561198305494036#!/compare/1561939200/1562025600

https://backpack.tf/profiles/76561198138340148#!/compare/1558915200/1562025600

Most likely not the correct buyer.

https://i.imgur.com/gYhuSFE.png - labelled as 10 keys

Gambled up until the next bot purchase.

#3

Untraceable

https://backpack.tf/profiles/76561197963396109#!/compare/1561939200/1562112000

https://backpack.tf/profiles/76561198335791307#!/compare/1562025600/1562112000

https://i.imgur.com/gYhuSFE.png - labelled as 10 key + 6 ref purchase (~10 keys)

#4

Untraceable

https://backpack.tf/profiles/76561198334598690#!/compare/1562544000/1562630400

https://backpack.tf/profiles/76561198027152204#!/compare/1562025600/1562630400

https://i.imgur.com/gYhuSFE.png - labelled as 10 keys + 47 ref (~11 keys)

#5

Untraceable

https://backpack.tf/profiles/76561198105778194#!/compare/1562544000/1562630400

https://backpack.tf/profiles/76561198080179568#!/compare/1562544000/1562630400

Sellers:

https://i.imgur.com/PYAjiY2.png

https://backpack.tf/item/7510005647 - ~9.9 keys

https://backpack.tf/item/6386255812 - 10 keys

https://backpack.tf/item/5794453802 - ~10.4 keys

Sales at:

8.5

10 (3x)