Resuggestion, thanks to Jarool & Mindacos for the info!

Sale 1:

https://backpack.tf/profiles/76561198292180626#!/compare/1581552000/1588723200

https://backpack.tf/profiles/76561198933270485#!/compare/1581552000/1581638400

Untrace

sale 2:

https://backpack.tf/profiles/76561198850274253#!/compare/1582502400/1582588800

https://backpack.tf/profiles/76561198120845968#!/compare/1582156800/1582588800

https://backpack.tf/profiles/76561198850274253#!/compare/1582502400/1582588800

Tradeback

sale 3:

https://backpack.tf/profiles/76561198021055079#!/compare/1588636800/1588723200

https://backpack.tf/profiles/76561198220174679#!/compare/1588723200/1588809600

Keys, probably 13.

sale 4:

https://backpack.tf/profiles/76561198125247757#!/compare/1588118400/1588204800

https://backpack.tf/profiles/76561198012204846#!/compare/1588118400/1588723200

Bulky

Sale 5:

https://marketplace.tf/items/tf2/30054;5;u61

$19 / $1.75 = 10.86 keys

$18 / $1.75 = 10.29 keys

$18.89 / $1.69 = 11.18 keys

Jarool's Part:

mine sold for $24 on marketplace.

https://marketplace.tf/items/tf2/30054;5;u61

don't really remember my B/O prior to listing on marketplace, i think it was 12, bot.tf listings don't show anything either.

Mindacos' Part:

Another marketplace sale happened at $28.89(~15 Keys using 1.91 value):

https://marketplace.tf/items/tf2/30054;5;u61

Given Jarool's sale at $24, 10-15 doesn't seem too out of place here.