This might take the cake for worst effect in the game

Sale #1:

https://backpack.tf/item/16591304475

https://backpack.tf/profiles/76561198106956828#!/compare/1768348800/1768435200 ~ 40 keys pure

https://backpack.tf/profiles/76561197996232783#!/compare/1768348800/1768435200

Sale #2:

https://backpack.tf/item/16518611819

https://backpack.tf/profiles/76561198171032862#!/compare/1765843200/1764374400

https://backpack.tf/profiles/76561197999173629#!/compare/1765843200/1765756800 ~ bulk

Sale #3:

https://backpack.tf/item/16506897935

https://backpack.tf/profiles/76561198877565874#!/compare/1765584000/1765670400

https://backpack.tf/profiles/76561197972510204#!/compare/1765584000/1765670400 ~ sold with a Twilight Snowfall Shoestring Santa for ?

Sale #4:

https://backpack.tf/item/16499949787

https://backpack.tf/profiles/76561198073376693#!/compare/1766534400/1767225600 ~ no matches

https://backpack.tf/profiles/76561198310750043#!/compare/1766534400/1766620800

Sale #5:

https://backpack.tf/profiles/76561198986698138#!/compare/1766102400/1767052800 ~ no matches

https://backpack.tf/profiles/76561198073376693#!/compare/1765670400/1766102400

This one is interesting, looking at both sides, it seems that pawfreak may give him the Strange Specialized Killstreak Australium Tomislav + keys, and then Eradicator uses that to upgrade to the Pro KS one (as the spec ks one goes to a qs store bot, then he recieves the pro ks one same day from a qs store bot)