Sale #1:

https://backpack.tf/profiles/76561197974567850#!/compare/1550707200/1550793600

Sold for 22 keys and 18 ref.

22 keys

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Sale #2:

https://backpack.tf/profiles/76561198101534768#!/compare/1550966400/1551052800

Sold for 22 keys.

22 keys

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Sale #3:

https://backpack.tf/profiles/76561198024867201#!/compare/1547769600/1547856000

Sold for 27 keys.

27 keys

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Sale #4:

https://backpack.tf/profiles/76561198024867201#!/compare/1546041600/1546128000

Unsure.

Seller at 24 keys (x2) determines low-end (https://i.imgur.com/xbQDsns.png). 22 keys is quickbuying price, not using.