Marketplace Sales:

https://marketplace.tf/items/tf2/30119;5;u11

$140 on April 15th

$85.05 on May 20th, excluding as it would’ve gone to a buy order, and is most likely lower than buy orders.

https://manic.tf/keyprice/?at=2019-04-15 - $140 / $1.77 = 79.10 keys, no B/O listed on bot.tf

X = 79

Other Sales:

https://backpack.tf/item/7577160180 (#1)

https://backpack.tf/item/7424860462 - marketplace

https://backpack.tf/item/4991521322 - marketplace

#1

Bulk for Secret TC

https://backpack.tf/profiles/76561198137408503#!/compare/1559865600/1560384000

https://backpack.tf/profiles/76561198129552058#!/compare/1560297600/1560384000

Sellers:

https://i.imgur.com/GyNhj5m.png

https://backpack.tf/item/6674277243 - 70 keys

https://backpack.tf/item/7577160180 - 89 keys

https://backpack.tf/item/7424860462 - 89 keys, listed for ~69 keys worth on marketplace

https://backpack.tf/item/7342161018 - 97 keys

Sales at:

79

Seller at 70, another for ~69 on marketplace. Using 70 as the low-end.

Going with 70-79.