Using last month.

Technically in-date, but the change is larger than 15%.

Sales 1-3:

Sold for $13.50, $13, and $12 on marketplace.tf

https://marketplace.tf/items/30816;5;u3001

https://backpack.tf/item/5401875350 - no outpost

Couldn’t find the other item histories.

http://manic.tf/keyprice/?at=2018-08-21 - $12 / $1.9 = 6.32 keys

http://manic.tf/keyprice/?at=2018-08-29 - $13.5 / $1.88 = 7.18 keys

http://manic.tf/keyprice/?at=2018-09-08 - $13 / $1.88 = 6.91 keys

X = 7 (2x)

X = 6.5

Other Sales:

https://backpack.tf/item/5738766320 (#1)

https://backpack.tf/item/5555931201 (#2)

https://backpack.tf/item/5401875350 (#3)

https://backpack.tf/item/5208538429 (#4 & #5)

https://backpack.tf/item/5605489683 - SCM

https://backpack.tf/item/5228182261 - marketplace.tf

https://backpack.tf/item/6742566342 - mannco.trade/scammer

#1

Untraceable

https://backpack.tf/profiles/76561198119577257#!/compare/1536796800/1537228800

https://backpack.tf/profiles/76561198363395191#!/compare/1536796800/1536883200

#2

Untraceable, appears to be bulk

https://backpack.tf/profiles/76561198346116536 (rate limited exceeded, doesn’t matter as it’s bulk anyways

https://backpack.tf/profiles/76561198309716916#!/compare/1535500800/1535760000

#3

Untraceable

https://backpack.tf/profiles/76561198176511011#!/compare/1536105600/1536364800

https://backpack.tf/profiles/76561198002757046#!/compare/1536278400/1536364800

#4

Untraceable

https://backpack.tf/profiles/76561198350588571#!/compare/1536883200/1536969600

https://backpack.tf/profiles/76561198080001294#!/compare/1530662400/1536969600

#5

Untraceable

https://backpack.tf/profiles/76561198080001294#!/compare/1530662400/1536969600

https://backpack.tf/profiles/76561198397249586#!/compare/1536883200/1536969600

Sellers:

https://i.imgur.com/021Xm9o.png

https://i.imgur.com/cJNzx1I.png

https://backpack.tf/item/5636082026 - ~6.42 keys

https://backpack.tf/item/5401875350 - ~6.42 keys

https://backpack.tf/item/5738766320 - ~6.42 keys

https://backpack.tf/item/5228182261 - ~8.23 keys

https://backpack.tf/item/5195041338 - ~8.23 keys

https://backpack.tf/item/5204289871 - ~8.23 keys

https://backpack.tf/item/6968678440 - ~8.28 keys

https://backpack.tf/item/6070585091 - 9 keys

https://backpack.tf/item/5285903049 - 12 keys

Sales at:

6.5

7 (2x)

https://bot.tf/stats/item?def=30816&q=5&ef=Showstopper&craft=1&aus=0&ks=0

https://i.imgur.com/x8VWEjO.png

Nothing on bot.tf