Cold-Hearted

https://backpack.tf/item/520996403

Sale 1) Sold for 22 Keys

https://backpack.tf/profiles/76561198267189538#!/compare/1558224000/1558310400

https://backpack.tf/item/1888666395

Sale 2) Sold + Blizzardy Storm Hustler's Hallmark + Kazotsky Kick for a Blizzardy Storm Federal Casemaker

https://backpack.tf/profiles/76561198113276430#!/compare/1561507200/1561680000

https://backpack.tf/profiles/76561198156375472#!/compare/1561248000/1561680000

Using this to Mini the Casemaker for something else.

Sale 3) Sold for 20 Keys

https://backpack.tf/profiles/76561198156375472#!/compare/1562544000/1562630400

Low outlier.

Sale 4) Quicksold for 21 Keys

https://backpack.tf/profiles/76561198190577279#!/compare/1562544000/1562630400

https://backpack.tf/item/1043463694

Sale 5) Sold to a buy order for 20 Keys + 26 Refined

https://backpack.tf/profiles/76561198337734785#!/compare/1561939200/1562025600

https://backpack.tf/item/1151125939

Sale 6) Sold for 23 Keys

https://backpack.tf/profiles/76561198081270783#!/compare/1558656000/1558742400

Sale 7) ?

https://backpack.tf/profiles/76561198329718164#!/compare/1559260800/1559347200

Sale 8) Sold for 20 Keys to a buy order

https://backpack.tf/profiles/76561198126114757#!/compare/1560729600/1560902400

https://backpack.tf/profiles/76561198074890690#!/compare/1560643200/1560729600

https://imgur.com/a/Yd2PvPC

https://marketplace.tf/items/tf2/152;5;u30 - Sold for $49.99 when Keys were ~$1.81 each

https://marketplace.tf/items/tf2/5021;6

49.99 / 1.81 = 27.6, which rounds to 28 Keys

https://imgur.com/a/uqWMt6X - 1 Day Seller at 24 Keys and a 10 Day Seller at 26 Keys suggest the Marketplace sale at 28 is high

https://backpack.tf/item/1102888953

https://backpack.tf/item/1888666395

Taking 21 - 23, since the sales at 20 were buy order sales and the buyer in sale 3 quicksold for 21.

That said, I'm keeping 21 because of the numerous sales at 20.