Sale #1:

https://bot.tf/stats/item?def=1197&q=5&ef=Acidic+Bubbles+of+Envy&craft=1&aus=0&ks=0

https://backpack.tf/profiles/76561198335791307#!/compare/1551481200/1551567600

Sold for 21 keys.

21 keys

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Sale #2:

https://backpack.tf/profiles/76561198335791307#!/compare/1547938800/1548025200

Sold for 14 keys and 10 ref.

14 keys

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Sale #3:

https://marketplace.tf/items/1197;5;u3017

Sold for $49.

$49 / $1.79 = ~27 keys

27 keys

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Sale #5:

https://marketplace.tf/items/1197;5;u3017

Sold for $12.10

$12.10 / $1.79 = ~7 keys

7 keys

14 keys is too low, as quickbuyers will buy for a key higher. 7 keys is too low for obvious reasons.