Team Plasma

https://backpack.tf/item/268589630

Sale 1) Sold for an Infernal Smoke Burstchester (65 Keys)

https://backpack.tf/profiles/76561198082931104#!/compare/1500595200/1500681600

Burstchester Mini

https://backpack.tf/suggestion/59ded755cf6c7568c135103c - 65 Keys

https://backpack.tf/item/224410487

Sale 2) Sold for 66 Keys + ~10 Keys of Tour of Duty Tickets + ~1 Key of Refined

https://backpack.tf/profiles/76561197993383111#!/compare/1503446400/1503532800

66 + 10 + 1 = 77 Keys

Sale 3) Sold + Cloud 9 Bonk Boy for a Scorching Flames Le Party Phantom

https://backpack.tf/profiles/76561198135649925#!/compare/1504224000/1504310400

There's no Mini for the Phantom.

https://marketplace.tf/items/339;5;u15 - Sale at $179.99

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key - Keys were $1.93 at the time

179.99 / 1.93 = 93 Keys. This sale is a high Outlier.

Rounding 77 to 75 Keys.