This is shocking.

http://backpack.tf/item/5221890240

Sale 1) Sold for 22 Keys

http://backpack.tf/profiles/76561198150952295#!/compare/1483401600/1483660800 - Seller's Backpack

http://backpack.tf/profiles/76561198174203179#!/compare/1483574400/1483660800 - Buyer's Backpack

Only 5 Keys show in the Seller's backpack because the other 17 were sold for the Australium Grenade Launcher.

Low Outlier.

Sale 2) Sold + 5 Keys for a Sulphurous Your Worst Nightmare

http://backpack.tf/profiles/76561198079631972#!/compare/1483660800/1483747200 - Buyer's Backpack

High Outlier.

Sale 3) Sold for a Professional Killstreak Australium Grenade Launcher (~25 Keys) + Professional Killstreak Australium Stickybomb Launcher (~21 Keys)

http://backpack.tf/profiles/76561198079631972#!/compare/1483833600/1483920000

25 + 21 = 46 Keys

Sale 4) Sold for a Morning Glory Honcho's Headgear (57 Keys)

http://backpack.tf/profiles/76561198055331437#!/compare/1483920000/1484006400

Honcho's Mini

http://backpack.tf/profiles/76561198108608612#!/compare/1480982400/1481068800 - Sold for a Death at Dusk Greased Lightning

http://backpack.tf/profiles/76561198115325995#!/compare/1485043200/1485129600 - Sold for an Anti-Freeze Frenchman's Beret (50 Keys)

http://backpack.tf/profiles/76561198055331437#!/compare/1484092800/1484265600 - Sold for a Cloudy Moon Defiant Spartan (64 Keys)

Taking 57 Keys

Defiant Spartan Micro

http://backpack.tf/profiles/76561198055331437#!/compare/1486166400/1486252800 - Sold for a GE Tartan Spartan (60 Keys) + ~4 Keys of Items

Tartan Spartan Macro

http://backpack.tf/profiles/76561198002186909#!/compare/1485993600/1486080000 - Sold for a Frostbite Baker (60 Keys)