Sale 1:

Sold for 20 keys

Seller: https://backpack.tf/profiles/76561198114402400#!/compare/1549411200/1549497600

Buyer: https://backpack.tf/profiles/76561198074118996#!/compare/1549238400/1549497600

https://backpack.tf/item/6749880230

X = 20

Sale 2:

Sold for Nuts n Bolts Sola Topi (Suggestion at 7.75) + Stormy Coupe (Suggestion at 9)

Seller: https://backpack.tf/profiles/76561198024867201#!/compare/1545523200/1545609600

Buyer: https://backpack.tf/profiles/76561198825833809#!/compare/1545177600/1545609600

https://backpack.tf/item/6749880230

X = 17

Sale 3:

Sold for Stormy Storm Hot Dogger (Suggestion at 17) + 4 ref

Seller: https://backpack.tf/profiles/76561198061275415#!/compare/1547424000/1547510400

Buyer: https://backpack.tf/profiles/76561198167580668#!/compare/1547424000/1547510400

https://backpack.tf/item/6964750484

X = 17

Marketplace Sales:

https://marketplace.tf/items/30976;5;u7

https://manic.tf/keyprice/?at=2018-12-25 - $32 / $1.8 = 17.78 keys

https://manic.tf/keyprice/?at=2019-01-04 - $49.99 / $1.76 = 28.40 keys

https://manic.tf/keyprice/?at=2019-03-02 - $50 / $1.79 = 27.93 keys

X = 28 (2x)

X = 18

Other Sales:

https://backpack.tf/item/6964750484 (#1)

https://backpack.tf/item/6868980256 (#2)

https://backpack.tf/item/6749880230 (#3)

https://backpack.tf/item/6749083525 (#4-6)

https://backpack.tf/item/7420291822 - Scammed/gambled/unusable

https://backpack.tf/item/6763821466 - scammer

#1

Untraceable

https://backpack.tf/profiles/76561198083330469#!/compare/1547251200/1548115200

https://backpack.tf/profiles/76561198061275415#!/compare/1547164800/1547251200

#2

Bulk for Blizzardy Tundra

https://backpack.tf/profiles/76561198146477608#!/compare/1552003200/1552176000

https://backpack.tf/profiles/76561197964171516#!/compare/1551916800/1552003200

#3

Bulk for Scorching Bonk Leadwear

https://backpack.tf/profiles/76561198057855475#!/compare/1548115200/1548288000

https://backpack.tf/profiles/76561198114402400#!/compare/1548201600/1548288000

#4

Sold for an unusual scattergun

https://backpack.tf/profiles/76561197994697258#!/compare/1545350400/1545436800

https://backpack.tf/profiles/76561198364851711#!/compare/1545350400/1545436800

Can be used on the scatter if not too low there

#5

Sold for Planets Backwards Ballcap

https://backpack.tf/profiles/76561198364851711#!/compare/1545436800/1545523200

https://backpack.tf/profiles/76561198002757046#!/compare/1545436800/1545523200

Would be too low If used here (given sellers on the ballcap), and too high if used on the ballcap.

#6

Untraceable

https://backpack.tf/profiles/76561198002757046#!/compare/1545436800/1545523200

https://backpack.tf/profiles/76561198060775575#!/compare/1527379200/1550707200

Stormy Storm Coupe:

https://backpack.tf/suggestion/5c85d73467807208f4153a65

Nuts n’ Bolts Sola Topi:

https://backpack.tf/suggestion/5c85ed12d381727943586326

Stormy Hot Dogger:

https://backpack.tf/suggestion/5c860291d3817208100fa7e7

Sales at:

17 (2x)

18

20

28 (2x)

The 28 key sales are outliers, excluding them.

Going with 17-20.