Back again.

Sale 1: Unknown, likely gambled

https://backpack.tf/profiles/76561198353251333#!/compare/1568419200/1568505600

https://backpack.tf/profiles/76561198076144288#!/compare/1568332800/1568419200

Sale 2: Sold for 16 keys

https://backpack.tf/profiles/76561198076144288#!/compare/1568332800/1568419200

https://backpack.tf/profiles/76561198130121169#!/compare/1570060800/1570147200

Sale 3: Don't know

https://backpack.tf/profiles/76561198130121169#!/compare/1570579200/1571875200

https://backpack.tf/profiles/76561198103312296#!/compare/1571788800/1571875200

Sale 4, 5 & 6:

Sold for 30.99 on september 14

Sold for 49.96 on september 26 [https://backpack.tf/item/318127466 ]

Sold for 27 on october 13

https://marketplace.tf/items/tf2/101;5;u11

30.99/1.84 = 16.84 rounding to 17 keys

49.96/1.83 = 27.3 rounding to 27 keys

27/1.82 = 14.83 rounding to 15 keys

Sale 7: Sold with 5.23 keys for dbd boonie

https://backpack.tf/profiles/76561198236007746#!/compare/1571875200/1571961600

https://backpack.tf/profiles/76561198103312296#!/compare/1571875200/1571961600

Taking it over there, fewer sales to use there.

Classifieds:

https://gyazo.com/23130d22e0b3a7e5786e4ac0fa0c8897

Marketplace:

https://marketplace.tf/items/tf2/101;5;u11

Seller at 45 dollars for more than 2 weeks

https://backpack.tf/item/232781332

45 is less than sale 5, which is 49.96 dollars.

Conclusion:

Sale at 16. Marketplace sales at 15, 17, and 27.

Seller on marketplace has been there for over 2 weeks, at a lower price than 27 keys.

Taking 15-17 keys.