Sale #1:

https://backpack.tf/profiles/76561198112336424#!/compare/1542067200/1542153600

Sold for 25 keys

25 keys

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Sale #2:

https://marketplace.tf/items/96;5;u19

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

Sold for $56.99

$56.99 / $1.81 = ~31 keys

31 keys

Sellers starting at 29 keys, 25 is fine despite 24 key buyer due to the limited difference.