Thanks go to The Real Slim Strange and Blaze.xTH3RM4Lx.

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

The Nether Void Party Trick, while unpriced, is currently being sold for slightly above 5 keys. https://gladiator.tf/listings/61857848f9b6f863acd0d3c0

11.8+1.7+5.2=18.7

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

Sold for 34.99 USD on September 28th.

34.99/1.83=19.12

Sold for 34.50 USD on October 3rd.

34.50/1.83=18.85

Sold for 34.99 USD on October 9th.

34.99/1.87=18.71

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

The rest:

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.

All sales:

18

18.7

18.71

18.85

19.12

19.3

Taking 18-19 keys.