This is pretty. I want this.

https://backpack.tf/item/1031944499

Sale 1) Sold for $350 when Keys were ~$1.77 each

https://marketplace.tf/items/393;5;u9;strange

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

350 / 1.77 = 197.74, which I'll round to 200 Keys

Sale 2) Sold for 100 Keys + Clairvoyance Tundra Top (83 Keys) + Open Mind Universal Translator (58 Keys)

https://backpack.tf/profiles/76561198021272428#!/compare/1542067200/1542153600

100 + 83 + 58 = 241, which rounds to 240 Keys

Clairvoyance Tundra Top Mini

https://backpack.tf/suggestion/5c24441a44325a0843313515 - 83 Keys

Open Mind Universal Translator Mini

https://backpack.tf/suggestion/5c244207cf6c750e9f73e066 - 58 Keys with Sale 1 being 65 Keys. Waiting for tonk to provide a picture to confirm it.

Sale 3) Sold + Spooky Night Didgeridrongo + Professional Killstreak Australium SMG (~9.5 Keys) for a Disco Beat Down Polar Pullover (330 Keys)

https://backpack.tf/profiles/76561198022071751#!/compare/1541980800/1542153600

https://backpack.tf/profiles/76561197988768189#!/compare/1542067200/1542153600

High outlier.

Drongo Mini

https://backpack.tf/profiles/76561198116110446#!/compare/1541289600/1541376000 - Sold for a Haunted Ghosts Puffy Polar Cap (21.5 Keys)

https://backpack.tf/profiles/76561198021055079#!/compare/1545264000/1545350400 - Sold for 29 Keys? IDs match. Waiting for Jarool to confirm.

Polar Pullover Mini

https://backpack.tf/suggestion/5c2a6cdbcf6c755b5731b7e7 - 330 Keys

Sale 4) Sold for $350 when Keys were ~$1.66 each

https://marketplace.tf/items/393;5;u9;strange

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

350 / 1.66 = 210.84, which I'll round to 210 Keys

https://backpack.tf/item/314355361 - Duped

Sale 5) Sold for $390 when Keys were ~$1.71 each

https://marketplace.tf/items/393;5;u9;strange

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

390 / 1.71 = 228.07, which I'll round to 230 Keys

https://backpack.tf/item/821798418 - Duped

Sale 6) Sold for a Duped Circling Heart Villain's Veil (210 Keys) + ~41 Keys of Items

https://backpack.tf/profiles/76561198021272428#!/compare/1544400000/1544486400 - Seller's Backpack

https://backpack.tf/profiles/76561198210322871#!/compare/1544400000/1544486400 - Buyer's Backpack

210 + 41 = 251, which I’ll round to 250 Keys

Duped Circling Heart Villain’s Veil Mini

Sold for a Duped Burning Flames Troublemaker's Tosslecap (110 Keys) + ~98 Keys of Australiums and a Vintage Pro KS Luger

https://backpack.tf/profiles/76561198061440669#!/compare/1540425600/1540512000

110 + 98 = 208, which rounds to 210 Keys

Duped Burning Flames Troublemaker's Tosslecap Micro

https://backpack.tf/profiles/76561198179707937#!/compare/1541116800/1541289600 - Sold for a Disco Beat Down Hong Kong Cone

https://backpack.tf/profiles/76561198100050147#!/compare/1543968000/1544054400 - Bulk sale for a Cloudy Moon Patriot Peak

https://backpack.tf/profiles/76561198328624791#!/compare/1543881600/1544054400 - Bulk sale for a Harvest Moon Pyromancer's Mask

https://backpack.tf/profiles/76561198054862332#!/compare/1544400000/1544572800 - Bulk sale for a Harvest Moon Team Captain

https://backpack.tf/profiles/76561198232041512#!/compare/1545436800/1545523200 - Sold for 110 Keys

https://imgur.com/a/IiCT9hp - Supreme confirming his purchase, since the above compare link shows 109 Keys.

https://backpack.tf/profiles/76561198099481645#!/compare/1540857600/1541203200 - Sold + ~20 Keys of Items for a Sunbeams Ballcap

https://backpack.tf/profiles/76561198113188320#!/compare/1541116800/1541203200 - Bulk sale

https://backpack.tf/profiles/76561198061779536#!/compare/1541289600/1541376000 - Sold for a Burning Flames Field Practice + 7 Keys

Using the Ballcap sale for the Ballcap and the Field Practice sale for the Field Practice. The HKC sale is high.