Edit: Found a Buyout on Sale 1

http://backpack.tf/item/3565175554

Sale 1) DBD Cannonball (42.5 Keys) + Blizzardy Cannonball (27 Keys) + 77 Refined (4 Keys) + 1 Key = 74.5 Keys

http://backpack.tf/profiles/76561198137762264/#!/compare/1455782400/1455868800

http://www.tf2outpost.com/trade/27847171 - Capped by the Buyout of 59 Keys (see the first comment)

Sale 2) Sold for a Flaming Lantern Western Wear (34 Keys) + 5 Keys

http://backpack.tf/profiles/76561198048431762/#!/compare/1456473600/1456560000

Western Wear Mini

http://backpack.tf/vote/id/5712db8b8667472fd47d0dec - Western Wear is 34 Keys

Sale 3) Sold for a Professional Killstreak Australium Scattergun + Cloud 9 Human Cannonball

http://backpack.tf/profiles/76561198080179568/#!/compare/1459209600/1459296000

http://www.tf2outpost.com/trade/28007236 - Capped by the Buyout of 70 Keys

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http://backpack.tf/item/2733128041

Sale 4) Sold for a Max's (29.5) + Terror-Watt Dread Knot + Strange Spec KS Backwoods Boomstick (~2) + an Unusual SMG

http://backpack.tf/profiles/76561198136099561/#!/compare/1456473600/1457078400

http://www.tf2outpost.com/trade/27918226 - Likely capped by the Buyout of 55 Keys

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http://backpack.tf/item/2650544612

Sale 5) Sold for 72 Keys

http://backpack.tf/profiles/76561198067902503/#!/compare/1455955200/1456214400

Sale 6) Sold for 90 Keys

http://www.tf2outpost.com/trade/27970399 - See the Buyer's comment

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http://backpack.tf/item/2428238730

Sale 7) Quicksold for 58 Keys

http://backpack.tf/profiles/76561198120505232/#!/compare/1454400000/1455091200

Sale 8) Sold for 60 Keys

http://backpack.tf/profiles/76561198240000948/#!/compare/1458370800/1458457200

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Ruling Sales 2 and 4 Outliers because of Sale 7 being a Quicksell.

Ruling Sale 6 an Outlier because of it's distance from the remaining 4 Sales (1, 3, 5 8)

That leaves 59 Keys, 60 Keys, 70 Keys, and 72 Keys.