I feel like this hat would look very weird in person.

https://backpack.tf/item/5375247602

Sale 1) Sold + ~5 Keys of Items for a Starstorm Insomnia Nasty Norsemann (21.5 Keys)

https://backpack.tf/profiles/76561198400019669#!/compare/1512604800/1512691200

21.5 - 5 = 16.5, which rounds to 17 Keys

https://backpack.tf/item/5384898608

Sale 2) Sold for a Ghastly Ghosts Most Wanted (21.5 Keys) + ~1.5 Keys of Items

https://backpack.tf/profiles/76561198142199367#!/compare/1511827200/1511913600 - Seller's Backpack

https://backpack.tf/profiles/76561198155183519#!/compare/1511827200/1511913600 - Buyer's Backpack

The Most Wanted was then quickly sold for the Silver Cyclone Mannrobics.

21.5 + 1.5 = 23 Keys

Sale 3) Sold for a Nuts and Bolts Bolted Bicorne + Orbiting Planets Tam O'Shanter

https://backpack.tf/profiles/76561198228255636#!/compare/1512691200/1512777600

Fits in the range because there are quickbuyers at 16.66 Keys combined for both ---> https://imgur.com/a/e5dkI

There's no good Mini for the Bicorne, anyway. Its only other sale I can find is for a Planets Mirror - its only other sale I can find is for a SGG Results Are In

Sale 4) Sold for a Purple Confetti Ol' Snaggletooth + ~0.3 Keys of Items

https://backpack.tf/profiles/76561198173389367#!/compare/1512777600/1512864000

Fits in the range.

Snaggle Mini

https://backpack.tf/profiles/76561198066195760#!/compare/1511481600/1511654400 - Sold for a Vivid Plasma Big Elfin Deal (17.5 Keys) - NOT THE KEYS.

https://backpack.tf/profiles/76561198428014176#!/compare/1511481600/1511654400 - Sold for a Circling TF Logo Milkman (around 15 - 16 Keys)

Milkman Micro

https://backpack.tf/profiles/76561198275369526#!/compare/1511222400/1511395200 - Sold for 14 Keys + 17 Refined

https://backpack.tf/profiles/76561198182717894#!/compare/1511308800/1511395200 - Sold for an Aces High Voodoo Juju + 4 Keys

http://www.tf2outpost.com/trade/29452887 - Capped by the Buyout of 16 Keys

https://backpack.tf/profiles/76561198102058669#!/compare/1512086400/1512259200 - Sold for a Circling TF Logo Blast Defense (<20 Keys)

https://backpack.tf/profiles/76561198192241101#!/compare/1512345600/1512432000 - Sold for a Circling Peace Sign Ol' Snaggletooth (<20 Keys)

Sale 5) Sold + 2 Keys for a Green Energy Elf Esteem (21 Keys)

https://backpack.tf/profiles/76561198182717894#!/compare/1513036800/1513123200

21 - 2 = 19 Keys

Other Sales credits to Mindacos

https://backpack.tf/profiles/76561198182717894#!/compare/1513123200/1513209600 - 15 Keys qs

https://backpack.tf/profiles/76561198045692488#!/compare/1513123200/1513209600 - 18 Keys?

https://imgur.com/a/YsRp8 - The sellers at 16 and 18 sold (the above 2 sales)

There is still a 1 month unsold at 19 Keys and a 4 month unsold at 21 Keys to rule 23 high.

https://backpack.tf/item/5524363757 - 19 Seller

https://backpack.tf/item/5447885716 - 21 Seller