Sale #1:

https://marketplace.tf/items/318;5;u32/Orbiting%20Planets%20Prancer's%20Pride

https://i.imgur.com/Th61gvb.png

$17.99 / $1.77 = ~10.2 keys

10 keys

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Sale #2:

https://marketplace.tf/items/318;5;u32/Orbiting%20Planets%20Prancer's%20Pride

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

$19.68 / $1.81 = ~10.9 keys

11 keys

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Sale #3:

https://backpack.tf/profiles/76561198347495247#!/compare/1548547200/1548806400

Sold with ~3 keys for a Smoking Airdog (11 keys)

11 - 3 = 8

~8 keys

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Minis:

Smoking Airdog:

https://marketplace.tf/items/30767;5;u35

https://i.imgur.com/tajD88w.png

$19.50 / $1.75 = ~11.1 keys

11 keys

Can't find any other good sales that aren't quicksales, any additional proof would be appreciated.