Sale #1

https://backpack.tf/profiles/76561199069692074#!/compare/1603670400/1603756800

Strange Specialized Killstreak Australium Knife (23 Keys) + 4 Keys = 27 Keys [Needs a mini].

Sale #2

https://backpack.tf/profiles/76561199069692074#!/compare/1602115200/1602201600

https://backpack.tf/profiles/76561198796395930#!/compare/1602115200/1602288000

Circling Heart Ye Olde Baker Boy (28 Keys) + 6 Keys for a Scorching Flames Air Dog

Sale #3

https://backpack.tf/profiles/76561198368971101#!/compare/1603152000/1603238400

Confirmed with seller, he brought it for 21 Keys 44 ref, rounding to 22 Keys. Excluding lower than current buyers.

https://ibb.co/YPR69Pv

Sale #4

https://backpack.tf/profiles/76561198368971101#!/compare/1603324800/1603411200

Quicksell for 24 Keys, excluding.

Sale #5

https://backpack.tf/profiles/76561198089291231#!/compare/1603324800/1603411200

Found a quicksell price from the other seller with the bulk sales, excluding.

All the other sales were outdated, same with marketplace sales.

Current sellers at 28 Keys and buyers are higher at 23.28 Keys.

Summary:

22 Keys quicksell, excluding.

24 Keys quicksell, excluding.

27 Keys

28 Keys

Conclusion:

I'd go with a 27-28 Keys suggestion here, thank you.