Thanks go to The Real Slim Strange.

I bought it for a Spec. KS Lugermorph, a Nether Void Party Trick, and a Unique Balloonibouncer on August 17th.

https://imgur.com/a/kjC2FGh

https://backpack.tf/profiles/76561199119392127#!/compare/1629072000/1629158400

https://backpack.tf/profiles/76561198135737005#!/compare/1629072000/1629158400

The Lugermorph went for slightly below 12 keys. https://gladiator.tf/listings/611aa1f0ec451773d777715a

The Balloonibouncer went for 1 key and 43 ref. https://snapshots.tf/snapshot/611ae77138bcaca0d8a1a80e

I bought The Nether Void Party Trick taunt for 8 keys a few days earlier (anyone can use this for an NV Trick suggestion).

https://backpack.tf/profiles/76561198135737005#!/compare/1628726400/1628812800

11.8+1.7+8=21.5

Rounding it up to 22.

Mp.tf: https://marketplace.tf/items/tf2/30570;5;u3056

Sold for 34.99 USD on September 28th.

34.99/1.83=19.12

Mannco.store: https://mannco.store/item/440-shimmering-lights-unusual-taunt-pool-party

Sold for 32.24 USD on July 14th.

32.24/1.67=19.3

Rounding both to 19.

https://backpack.tf/item/9613494303 - Untraceable.

https://backpack.tf/item/4179295814 - Untraceable.

https://backpack.tf/profiles/76561198232041512#!/compare/1625356800/1625443200

https://backpack.tf/profiles/76561198006361327#!/compare/1622592000/1625443200 - 18 keys.

Sales:

18

19

19

22

Taking 18-22 keys.