Huff and Puff and blow the house down.

https://backpack.tf/item/7323131933

Sale 1) Bulk sale

https://backpack.tf/profiles/76561198120672630#!/compare/1555977600/1556064000

https://backpack.tf/item/7262102638

Sale 2) Bulk sale

https://backpack.tf/profiles/76561198038637602#!/compare/1556668800/1556755200

Sale 3) Sold for a Burning Flames Ze Goggles (45 Keys) + Duped Cloud 9 A Rather Festive Tree (26 Keys) + 2 Keys

https://backpack.tf/profiles/76561198150783829#!/compare/1558742400/1558828800

https://backpack.tf/profiles/76561198000102611#!/compare/1558656000/1558742400

45 + 26 + 2 = 73 Keys

Goggles Mini

https://backpack.tf/suggestion/5d13e1bcd38172421c4ff762 - 45 Keys

Tree Mini

https://backpack.tf/profiles/76561198067186749#!/compare/1554508800/1554595200 - Sold for 26 Keys. The Translator sold for the other 11.

https://imgur.com/a/iNFODYp - Buyout of 26 Keys

https://backpack.tf/profiles/76561198000102611#!/compare/1556928000/1557014400 - Sold for 26 Keys

https://imgur.com/a/ItgVc1u - Buyout of 26 Keys

https://backpack.tf/profiles/76561198119634686#!/compare/1555977600/1556064000 - Sold + 4 Keys for a Sunbeams Doctor's Sack

https://marketplace.tf/items/tf2/341;5;u58 - Sold for $60 and $59.99

https://imgur.com/a/dgnZZlW - 6 Day Seller at 29.5 Keys

Taking 26 Keys

Sale 4) Sold for a Harvest Moon Bloke's Bucket Hat

https://backpack.tf/profiles/76561198000102611#!/compare/1558742400/1558828800

Can be used for the Bucket.

https://marketplace.tf/items/tf2/30958;5;u115 - Sold for $135 when Keys were ~$1.82 each

https://marketplace.tf/items/tf2/5021;6

135 / 1.82 = 74.2, which rounds to 74 Keys