Resuggestion, thanks to Jarool & Itsy for the info!

Sale 1:

https://backpack.tf/profiles/76561198297167809#!/compare/1543449600/1543708800

https://backpack.tf/profiles/76561198862028218#!/compare/1543708800/1543795200

QS

Sale 2:

https://backpack.tf/profiles/76561198862028218#!/compare/1544745600/1544832000

https://backpack.tf/profiles/76561198290206794#!/compare/1544486400/1544918400

Untrace

Sale 3:

https://backpack.tf/profiles/76561198058569038#!/compare/1545955200/1546128000

https://backpack.tf/profiles/76561198203697487#!/compare/1543449600/1543622400

Sold for 6 keys

Sale 4:

https://backpack.tf/profiles/76561198203697487#!/compare/1543622400/1544054400

https://backpack.tf/profiles/76561198021055079#!/compare/1543622400/1543795200

QS?

Sale 5:

https://backpack.tf/profiles/76561198021055079#!/compare/1545091200/1545177600

https://backpack.tf/profiles/76561198055605045#!/compare/1544486400/1545868800

SCM

Sale 6:

https://backpack.tf/profiles/76561198055605045#!/compare/1545868800/1546732800

https://backpack.tf/profiles/76561198067780331#!/compare/1546041600/1547683200

Untrace

Sale 7:

https://backpack.tf/profiles/76561198021055079#!/compare/1549152000/1549238400

https://backpack.tf/profiles/76561197992416935#!/compare/1549843200/1550016000

Untrace

Sale 8:

https://backpack.tf/profiles/76561198335791307#!/compare/1546128000/1546300800

https://backpack.tf/profiles/76561198110575081#!/compare/1546128000/1546300800

Bought, then gift?

Sale 9:

https://backpack.tf/profiles/76561198068404730#!/compare/1547078400/1547337600

https://backpack.tf/profiles/76561198025795458#!/compare/1547164800/1547337600

Sold for 6 keys

Sale 10:

https://backpack.tf/profiles/76561198002757046#!/compare/1546819200/1546905600

https://backpack.tf/profiles/76561198282372085#!/compare/1546992000/1547078400

Bulky?

Sale 11:

https://backpack.tf/profiles/76561198282372085#!/compare/1550275200/1550361600

https://backpack.tf/profiles/76561198254487535#!/compare/1550275200/1551052800

Bulk

Sale 12:

https://backpack.tf/profiles/76561198232041512#!/compare/1550275200/1550361600

https://backpack.tf/profiles/76561198016070169#!/compare/1550275200/1550361600

Keys, qs?

Sale 13:

https://marketplace.tf/items/30762;5;u3022

$22.00 / $1.72 = 12.79 keys

Jarool's Part:

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

https://i.imgur.com/Vmbz3Gn.png

Sold for $32 AUD on the SCM (~$22.80 USD) after tax. B/O would've been 10.

Ity's Part:

Sale 12: I paid 10 Pure

https://backpack.tf/profiles/76561198016070169#!/compare/1550275200/1550361600

https://backpack.tf/profiles/76561198232041512#!/compare/1550275200/1550361600

https://imgur.com/xzGNb0g

Sales @:

6, 6, 10, 10, 12.79 keys

With the MPTF sale now being outdated, and 2 low sales that took some time,

Taking 6 - 10 keys