Party Control

https://backpack.tf/item/2368013862

Sale 1) Bulk sale for a Burning Flames Brotherhood of Arms

https://backpack.tf/profiles/76561198181652993#!/compare/1544918400/1545177600

Sale 2) Sold for $599.99 when Keys were ~$1.80 each

https://marketplace.tf/items/30329;5;u62

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key

599.99 / 1.80 = 333.3, which I'll round to 335 Keys

https://backpack.tf/item/3652546744

Sale 3) Sold + ~50 Keys of stuff for a Cauldron Bubbles Virtual Viewfinder (407 Keys)

https://backpack.tf/profiles/76561198232041512#!/compare/1549670400/1549756800

Fits in the range.

Viewfinder Mini

https://backpack.tf/suggestion/5c39c875cf6c75283726b075 - Foamy's comment makes Sale 1 340 Keys. 340 - 474 averages to 407 Keys.

https://backpack.tf/item/2595984058

Sale 4) Sold for a Frostbite Law (257 Keys) + 110 Keys + Frostbite Conquistador (47.5 Keys)

https://backpack.tf/profiles/76561198148495750#!/compare/1549756800/1549843200

https://imgur.com/a/WXjqE2w - Thanks, Eco

https://imgur.com/a/HTI6Lvx - Capped by the Buyout of 400 Keys

Law Mini

Sold for a Death at Dusk Cotton Head (145 Keys) + Green Energy Field Practice (74 Keys) + Morning Glory Bloke's Bucket Hat (38 Keys)

https://backpack.tf/profiles/76561198050062763#!/compare/1547510400/1547683200

https://cdn.discordapp.com/attachments/544945447748501514/544946655024119808/unknown.png - Thanks, Breezze

145 + 74 + 38 = 257 Keys

Cotton Head Micro

https://backpack.tf/suggestion/5c71cb1dd381727e18726ed4 - 145 Keys

Field Practice Micro

https://backpack.tf/suggestion/5c6473b944325a60e3351cf5 - 74 Keys

Frostbite Conquistador Mini

https://backpack.tf/suggestion/5c71cc7d6780724cd80a7186 - 47.5 Keys

https://backpack.tf/item/2760104516

Sale 5) Bulk sale

https://backpack.tf/profiles/76561198022071751#!/compare/1545955200/1546128000

https://backpack.tf/profiles/76561198114402400#!/compare/1546041600/1546128000

https://marketplace.tf/items/30329;5;u62 - Sold for $391.01

Low outlier.