Prepare the Diving Bell

https://backpack.tf/item/6896499346

Sale 1) ?

https://backpack.tf/profiles/76561198066187759#!/compare/1563494400/1566000000

https://backpack.tf/profiles/76561198095862827#!/compare/1563408000/1563494400

Sale 2) Sold for $44.75 when Keys were ~$1.83 each

https://marketplace.tf/items/tf2/397;5;u29

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

44.75 / 1.83 = 24.45, which rounds to 24 Keys

https://backpack.tf/item/612170697

Sale 3) Sold for 22 Keys

https://backpack.tf/profiles/76561198204380921#!/compare/1563753600/1564099200

Sale 4) Bulk sale for a Burning Flames Coldfront Commander

https://backpack.tf/profiles/76561198079504588#!/compare/1565222400/1565308800

Sale 5) Bulk sale for a Scorching Flames Shutterbug

https://backpack.tf/profiles/76561198129995083#!/compare/1565308800/1565395200

Sale 6) Sold + 7 Keys + ~1 Key of Items for a Nuts and Bolts Crone's Dome

https://backpack.tf/profiles/76561198103361840#!/compare/1565395200/1565481600

https://backpack.tf/profiles/76561198018148078#!/compare/1565395200/1565481600

Better for the Crone's.

Sale 7) Bulk sale for a Blizzardy Storm Team Captain

https://backpack.tf/profiles/76561198018148078#!/compare/1566172800/1566691200

Sale 8) Sold for a Dead Presidents Cold Killer + 8 Keys

https://backpack.tf/profiles/76561198102265073#!/compare/1566691200/1566777600

https://backpack.tf/profiles/76561198364475021#!/compare/1566691200/1566777600

Using for the Cold Killer.

Sale 9) Sold for a Disco Beat Down Warhood (16 Keys) + Circling Peace Sign Crack Pot (10 Keys) + 0.5 Keys of Items

https://backpack.tf/profiles/76561198364475021#!/compare/1566777600/1566864000

https://imgur.com/a/LAbf6oX - Capped by the Buyout of 26 Keys

Pot Mini

https://backpack.tf/suggestion/5d69e024d381726d1f461d18 - 10 Keys

Sale 10) Sold for a Searing Plasma Furious Fukaamigasa (17.5 Keys) + 4 Keys + ~0.5 Keys of Items

https://backpack.tf/profiles/76561198153536726#!/compare/1566864000/1566950400

https://backpack.tf/profiles/76561198189381361#!/compare/1566864000/1566950400

17.5 + 4 + 0.5 = 22 Keys

Furious Mini

https://backpack.tf/suggestion/5d68358fd3817258ca310a8a - 17.5 Keys

https://marketplace.tf/items/tf2/397;5;u29 - Sold for $35.86 (low) and $56.71 (high)