Not counting this one for the challenge, as i had it ready before hand. Also, was making it for a different reason.

Sale 1:

https://backpack.tf/profiles/76561198207837977#!/compare/1552435200/1552521600

https://backpack.tf/profiles/76561198515764827#!/compare/1552348800/1552521600

Sold for 8 keys

Sale 2:

https://backpack.tf/profiles/76561198515764827#!/compare/1549670400/1549756800

https://backpack.tf/profiles/76561198089697387#!/compare/1549670400/1549756800

Sold for ~8.5 keys

Sale 3:

https://backpack.tf/profiles/76561198089697387#!/compare/1549670400/1549756800

https://backpack.tf/profiles/76561198083111797#!/compare/1549497600/1549756800

Sold for ~8 keys

Sale 4:

https://backpack.tf/profiles/76561198083111797#!/compare/1550016000/1550534400

https://backpack.tf/profiles/76561198204028017#!/compare/1550016000/1550966400

Sold for ~9 keys

Sale 5:

https://backpack.tf/profiles/76561198204028017#!/compare/1551139200/1551830400

https://backpack.tf/profiles/76561198174632014#!/compare/1551398400/1551571200

Sold for MS Sorcery

Sorcery Mini:

https://backpack.tf/suggestion/5cd1f86cd381725a2f189444

Suggestion for 4 keys

Sale 6:

https://backpack.tf/profiles/76561198094230147#!/compare/1552003200/1552089600

https://backpack.tf/profiles/76561198312583107#!/compare/1551916800/1552003200

Sold for ~7.5 keys

Sale 7:

https://backpack.tf/profiles/76561198312583107#!/compare/1556150400/1556236800

https://backpack.tf/profiles/76561198429055852#!/compare/1556236800/1556236800/nearest

Sold for 8 keys

Sale 8:

https://backpack.tf/profiles/76561198429055852#!/compare/1556236800/1556323200

https://backpack.tf/profiles/76561198308606946#!/compare/1556150400/1556236800

Sold for 7 keys + ~2 keys in refined (sticky launcher sold for 13, other items sold for ref, which sold for the key:)

traceable here:

https://backpack.tf/profiles/76561198848842374#!/compare/1556150400/1556236800

using this ID: 7728312826

Total is 9 keys

Sale 9:

https://backpack.tf/profiles/76561198308606946#!/compare/1556323200/1556409600

https://backpack.tf/profiles/76561198043338415#!/compare/1556236800/1556409600

Bulk

Sale 10:

https://backpack.tf/profiles/76561198072374854#!/compare/1552867200/1552953600

https://backpack.tf/profiles/76561198074718149#!/compare/1552780800/1552867200

Untrace, anything after and before the first time scrap appears seems to be gambling.

sale 11:

https://backpack.tf/profiles/76561198056180801#!/compare/1554508800/1554681600

https://backpack.tf/profiles/76561198056180801#!/compare/1554508800/1554681600

Bulk

Sale 12:

https://backpack.tf/profiles/76561198056180801#!/compare/1554681600/1554768000

https://backpack.tf/profiles/76561198396959351#!/compare/1554336000/1554768000

Untrace

Sale 13:

https://backpack.tf/profiles/76561198377522406#!/compare/1555200000/1555372800

https://backpack.tf/profiles/76561198066566603#!/compare/1555200000/1555372800

Sold for ST SKullcracker + 1 key

Skullcracker Mini:

https://backpack.tf/suggestion/5cd7a33fd3817225b659c88d

Suggestion for 7.75 keys

Total is 8.75 keys

Sale 14:

https://backpack.tf/profiles/76561198066566603#!/compare/1555891200/1556323200

https://backpack.tf/profiles/76561198446548676#!/compare/1556236800/1556323200

Sold for Planets Sober(7.5) + ~0.5 keys in ref

Total is 8 keys

sale 15:

https://backpack.tf/profiles/76561198446548676#!/compare/1556236800/1556323200

https://backpack.tf/profiles/76561198145220298#!/compare/1555891200/1556323200

Sold with ~0.5 keys in sweets for ~9 keys

Total is 8.5 keys

Sale 16:

https://backpack.tf/profiles/76561198040186479#!/compare/1556323200/1556409600

https://backpack.tf/profiles/76561198369565670#!/compare/1556323200/1556409600

Untrace

Sale 17:

https://marketplace.tf/items/358;5;u32

$16.99 / $1.79 = 9.49 keys

$11.11 / $1.79 = 6.21 keys

Total sales @:

4, 7.5, 8, 8, 8, 8, 8.5, 8.5, 8.75, 9, 9

Unsold for ~8.25 for month+ (constantly relisted)

Buyers at 7 keys,

Taking 7.5 - 9 keys