Midnight Whirlwind Taunt: The Jumping Jack (4 - 4.35)
https://backpack.tf/stats/Unusual/Taunt%3A%20The%20Jumping%20Jack/Tradable/Craftable/3008

Sale 1)
https://backpack.tf/profiles/76561198027745463#!/compare/1563667200/1565395200 - Sold to a Quickbuyer for X Keys

Sale 2)
https://backpack.tf/profiles/76561198027745463#!/compare/1539129600/1560384000
https://backpack.tf/profiles/76561198852523690#!/compare/1560211200/1560384000 - SCM

Sale 3)
https://backpack.tf/profiles/76561198386571294#!/compare/1560124800/1560211200
https://backpack.tf/profiles/76561198852523690#!/compare/1560124800/1560211200 - Bulky

Sale 4)
https://backpack.tf/profiles/76561198363395191#!/compare/1561248000/1561334400
https://backpack.tf/profiles/76561198166414378#!/compare/1561593600/1563235200 - Likely sold via Mp.tf as dates don't match and seller transfered multiple items there
https://marketplace.tf/items/tf2/30845;5;u3008 - Sold for $9.30 / $1.85 = 5 Keys - Caps at Buyout
Buyout was 3 Keys 52.22 Ref which equals 4.06 Keys - https://bot.tf/stats/listings/4RL5N954 - Rounds to 4.05 Keys

Sale 5)
https://backpack.tf/profiles/76561198363395191#!/compare/1561161600/1561248000 - Sold to a Quickbuyer for X Keys

Sale 6)
https://backpack.tf/profiles/76561198023051867#!/compare/1561334400/1561420800
https://backpack.tf/profiles/76561198963466437#!/compare/1562284800/1563062400 - Maybe the other Mp.tf Sale
https://marketplace.tf/items/tf2/30845;5;u3008 - Sold for $9.30 / $1.85 = 5 Keys - Caps at Buyout
Buyout was 4 Keys - https://bot.tf/stats/listings/Y3V7PE64
The Bot Owner sold it Via Mp.tf so using the Bot's buyout should be okay, shows they were okay taking 4 Keys for it via bot

Sale 7)
https://backpack.tf/profiles/76561198334598690#!/compare/1560816000/1560902400 - Sold to a Quickbuyer for X Keys
https://bot.tf/stats/item?def=30845&q=5&ef=Midnight+Whirlwind&craft=1&aus=0&ks=0
https://gyazo.com/e2612b4cb4a6c265c4ffa39667ddf50d - Shows Sold for 3 Keys 20 Ref to a Buy order

Sale 8)
https://backpack.tf/profiles/76561198213860372#!/compare/1560816000/1560902400 - Sold for 2 Keys?

Sale 9)
https://backpack.tf/profiles/76561198363395191#!/compare/1561680000/1561766400
https://backpack.tf/profiles/76561198288038559#!/compare/1561680000/1562198400 - Untrace, maybe SCM

Sale 10)
https://backpack.tf/profiles/76561198819761397#!/compare/1559779200/1559865600
https://backpack.tf/profiles/76561198363395191#!/compare/1559779200/1559865600 - Sold to a Quickbuyer for X Keys

Sale 11)
https://backpack.tf/profiles/76561198074457853#!/compare/1562198400/1562630400
https://backpack.tf/profiles/76561198098422227#!/compare/1562112000/1563667200 - Untrace

Sale 12)
https://backpack.tf/profiles/76561198052560151#!/compare/1551225600/1562457600
https://backpack.tf/profiles/76561198080179568#!/compare/1561161600/1561248000 - Pretty sure it's the Mp.tf sale
https://marketplace.tf/items/tf2/30845;5;u3008 - Sold for $7.99 / $1.83 = 4.35 Keys
Can't trace a buyout

Sale 13)
https://backpack.tf/profiles/76561198354656940#!/compare/1559692800/1559779200
https://backpack.tf/profiles/76561198031993520#!/compare/1395558000/1564704000 - Untrace

Summary:
4, 4.05 and 4.35

Sellers are young ( https://gyazo.com/8f7d33e0c6a03f06fcf072f0c880cc52 ) and shouldn't make a lowend