Sale 1:

Sold for Disco Beat Down Your Worst Nightmare (~24.5) + Australium Sniper Rifle (~21.5 at the time)

Seller: https://backpack.tf/profiles/76561198053747026#!/compare/1542067200/1542153600

Buyer: https://backpack.tf/profiles/76561198206121028#!/compare/1541116800/1542153600

https://backpack.tf/item/7028724096

X = 46

Sales 2 & 3:

Sold for $46 & $45 on marketplace

https://marketplace.tf/items/30542;5;u7

https://manic.tf/keyprice/?at=2018-11-19 - $45 / $1.72 = 26.16 keys

https://manic.tf/keyprice/?at=2018-10-25 - $46 / $1.8 = 25.56 keys

X = 26 (2x)

Sale 4:

Bulk for Green Energy Rotation

Seller: https://backpack.tf/profiles/76561198155066949#!/compare/1541376000/1541462400

Buyer: https://backpack.tf/profiles/76561198053747026#!/compare/1541289600/1541376000

https://backpack.tf/item/7028724096

Sale 5:

Bulk-ish for Tesla Coil Muffs

Seller: https://backpack.tf/profiles/76561198053279911#!/compare/1542931200/1543017600

Buyer: https://backpack.tf/profiles/76561198093707809#!/compare/1542931200/1543017600

https://backpack.tf/item/7331247514

Better off being used on the muffs.

Sellers:

https://i.imgur.com/JwYkkNa.png

https://backpack.tf/item/7193412393 - 40 keys

https://backpack.tf/item/6050048411 - 44 keys

Sales at:

26 (2x)

46

https://i.imgur.com/S7iggah.png - Buyers at 26 and 28, excluding 26.

Aged seller at 40, using as low-end.

Going with 40-46.