Sale 1:

https://backpack.tf/profiles/76561198035746146#!/compare/1569888000/1570579200

https://backpack.tf/profiles/76561198044684270#!/compare/1570492800/1570579200

QS

sale 2:

https://backpack.tf/profiles/76561198866685546#!/compare/1565913600/1566000000

https://backpack.tf/profiles/76561198432461884#!/compare/1565395200/1566000000

https://backpack.tf/profiles/76561198971805272#!/compare/1565913600/1566000000

https://backpack.tf/profiles/76561198972279551#!/compare/1564012800/1566000000

Gambling?

sale 3:

https://backpack.tf/profiles/76561198322278232#!/compare/1566172800/1567728000

https://backpack.tf/profiles/76561198130266837#!/compare/1569110400/1570147200

Untrace

sale 4:

https://backpack.tf/profiles/76561198249206656#!/compare/1567123200/1567209600

https://backpack.tf/profiles/76561198051504085#!/compare/1566864000/1567209600

Sold for ~8.5 keys

Sale 5:

https://backpack.tf/profiles/76561198051504085#!/compare/1566864000/1567209600

https://backpack.tf/profiles/76561198068732040#!/compare/1567123200/1567209600

Sold for Smoking Noir(10.5)

Sale 6;

https://backpack.tf/profiles/76561198068732040#!/compare/1567123200/1567209600

https://backpack.tf/profiles/76561198142129821#!/compare/1567123200/1567209600

Sold for Searing Hedge + negligible sweets

sale 7:

https://backpack.tf/profiles/76561198255850192#!/compare/1567555200/1567641600

https://backpack.tf/profiles/76561198131081286#!/compare/1567382400/1567641600

Bulky

sale 8:

https://backpack.tf/profiles/76561198131081286#!/compare/1567728000/1567814400

https://backpack.tf/profiles/76561198169756327#!/compare/1567728000/1567814400

Sold for Stormy Merryweather(16)

https://bot.tf/stats/listings/YDLOLVZL

B/o of 15 keys, capping

Sale 9:

https://backpack.tf/profiles/76561198169756327#!/compare/1569110400/1569628800

https://backpack.tf/profiles/76561198986747837#!/compare/1569628800/1569715200

https://backpack.tf/profiles/76561198822711927#!/compare/1569196800/1569715200

https://backpack.tf/profiles/76561198064934368#!/compare/1567468800/1569715200

https://backpack.tf/profiles/76561198089253101#!/compare/1569628800/1569715200

Gambling

sale 10:

https://backpack.tf/profiles/76561198053557223#!/compare/1572480000/1572998400

https://backpack.tf/profiles/76561198129380689#!/compare/1572652800/1572739200

https://backpack.tf/profiles/76561198286784386#!/compare/1572652800/1572739200

https://backpack.tf/profiles/76561198040791634#!/compare/1572739200/1572825600

Untrace

sale 11:

https://backpack.tf/profiles/76561198154495510#!/compare/1566000000/1566086400

https://backpack.tf/profiles/76561198040464611#!/compare/1566000000/1566086400

Sold for Searing Gym Rat(15)

https://bot.tf/stats/listings/MGZ5O05Q

B/O of 14 keys, capping

Sale 12:

https://backpack.tf/profiles/76561198040464611#!/compare/1566086400/1566259200

https://backpack.tf/profiles/76561198309862404#!/compare/1566172800/1566259200

Untrace

sale 13:

https://backpack.tf/profiles/76561198309862404#!/compare/1566172800/1566259200

https://backpack.tf/profiles/76561198134902030#!/compare/1566172800/1566259200

Sold for Bubbling Toy Soldier

use there

Sale 14:

https://backpack.tf/profiles/76561198134902030#!/compare/1567296000/1567382400

https://backpack.tf/profiles/76561198277038758#!/compare/1567296000/1567382400

Bulky

sale 15 - 20:

https://marketplace.tf/items/tf2/30977;5;u7

$16 / $1.83 = 8.74 keys

$27.99 / $1.83 = 15.30 keys

$24.12 / $1.82 = 13.25 keys <--- https://backpack.tf/item/6747232654

$12.2 / $1.82 = 6.70 keys

$22.99 / $1.80 = 12.77 keys <---- https://backpack.tf/item/6862037118

$24.99 / $1.79 = 13.96 keys

Total sales @:

6.7, 8.5, 8.74, 10.5, 12.77, 13.25, 13.96, 14, 15, 15.30 keys

buyers up to ~8.5 keys,

3 month old seller at 15 keys,

1 month old seller at 13 keys,

https://i.imgur.com/Oph25yO.png

lets take 11 - 15 keys, conserving around unsold.