Sale #1:

https://mannco.store/item/8977

Sold for $90.

$90 / $1.78 = ~51 keys

51 keys

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Sale #2:

https://backpack.tf/profiles/76561198072374854#!/compare/1553472000/1553558400

Untraceable.

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Sale #3:

https://bot.tf/stats/item?def=167&q=5&ef=Haunted+Phantasm&craft=1&aus=0&ks=0

https://backpack.tf/profiles/76561198305494036#!/compare/1553468400/1553554800

Bought for 38 keys and 10 ref.

38 keys

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Sale #4:

https://bot.tf/stats/item?def=167&q=5&ef=Haunted+Phantasm&craft=1&aus=0&ks=0

https://backpack.tf/profiles/76561198305494036#!/compare/1553727600/1553814000

Sold for 45 keys.

45 keys

Sales:

38, 45, 51. Going with 51 keys due to a buyer at 50 keys (https://i.imgur.com/0y6qb85.png).