Sale 1:

https://backpack.tf/profiles/76561198213541049#!/compare/1588723200/1590624000

https://backpack.tf/profiles/76561198144089680#!/compare/1588982400/1589328000

untrace

sale 2:

https://backpack.tf/profiles/76561198144089680#!/compare/1589328000/1589500800

https://backpack.tf/profiles/76561198273988414#!/compare/1589328000/1589414400

https://backpack.tf/profiles/76561198260686830#!/compare/1589414400/1589500800

Untrace

sale 3:

https://backpack.tf/profiles/76561198260686830#!/compare/1589414400/1589500800

https://backpack.tf/profiles/76561198850274253#!/compare/1589414400/1589500800

QS

sale 4:

https://backpack.tf/profiles/76561198850274253#!/compare/1589673600/1589760000

https://backpack.tf/profiles/76561198040186479#!/compare/1589673600/1589760000

untrace

sale 5:

https://backpack.tf/profiles/76561198308987880#!/compare/1591747200/1591920000

https://backpack.tf/profiles/76561198305494036#!/compare/1591833600/1591920000

QS for ~6 keys

Sale 6:

https://backpack.tf/profiles/76561198305494036#!/compare/1591833600/1591920000

https://backpack.tf/profiles/76561198141187659#!/compare/1591833600/1591920000

Sold for ~7 keys (grouped with non matching ID ref)

Sale 9:

https://backpack.tf/profiles/76561198141187659#!/compare/1591833600/1591920000

https://backpack.tf/profiles/76561198055339823#!/compare/1592006400/1592092800

Untrace / MPTF?

Sale 10:

https://backpack.tf/profiles/76561199022645826#!/compare/1591833600/1592006400

https://backpack.tf/profiles/76561198839307425#!/compare/1591747200/1591833600

QS(?)

sale 11:

https://backpack.tf/profiles/76561198841279602#!/compare/1589932800/1590019200

https://backpack.tf/profiles/76561198116926113#!/compare/1589846400/1590019200

sold for ~7 keys

sale 12:

https://marketplace.tf/items/tf2/604;5;u56

$16.99 / $1.79 = 9.49 keys

$16.99 / $1.90 = 8.94 keys

$18.99 / $1.99 = 9.54 keys

$18.99 / $1.98 = 9.59 keys

Sale 16:

https://backpack.tf/profiles/76561198014326469#!/compare/1589414400/1589328000

https://backpack.tf/profiles/76561198305494036#!/compare/1589328000/1589414400

QS

Total sales @:

7, 7, 9, 9.5, 9.5, 9.5 keys

https://i.imgur.com/VXiwGHc.jpg

buyers up to ~7 keys,

seller for at least 3 days for 9 keys,

let's try 9 - 9.5 keys.