Wildcard

https://backpack.tf/item/629433039

Sale 1) Sold + ~6.5 Keys of Items for a Professional Killstreak Australium Rocket Launcher (~50 Keys)

https://backpack.tf/profiles/76561198088192753#!/compare/1527033600/1527120000

50 - 6.5 = 43.5, which rounds to 44 Keys

Low Outlier.

https://backpack.tf/item/1093041883

Sale 2) Sold for 58 Keys

https://backpack.tf/profiles/76561198074118789#!/compare/1524873600/1524960000

https://backpack.tf/item/1330248065

Sale 3) Bulk sale

https://backpack.tf/profiles/76561198083637551#!/compare/1522540800/1522713600

Sale 4) Bulk sale

https://backpack.tf/profiles/76561198054862332#!/compare/1523232000/1523318400

https://backpack.tf/item/780426717

Sale 5) Sold for a Green Energy Defiant Spartan (44 Keys) + Professional Killstreak Australium Ambassador (~13.5 Keys) + ~2 Keys of Items

https://backpack.tf/profiles/76561198292242424#!/compare/1521417600/1521504000

https://backpack.tf/profiles/76561198066198402#!/compare/1521331200/1521504000

44 + 13.5 + 2 = 59.5, which rounds to 60 Keys

Spartan Mini

https://backpack.tf/suggestion/5b10d51444325a6e95537f8a - 44 Keys