Using last month.

Sale 1:

Sold for 12 keys + ~1 key in metal

Seller: https://backpack.tf/profiles/76561198132741569#!/compare/1546646400/1546732800

Buyer: https://backpack.tf/profiles/76561198111088148#!/compare/1546732800/1546819200

https://backpack.tf/item/4527954810

X = 13

Sale 2:

Sold for 5 keys + ~4.5 keys in items (ToD tickets included on the buyer’s end)

Seller: https://backpack.tf/profiles/76561198316819529#!/compare/1545955200/1546041600

Buyer: https://backpack.tf/profiles/76561198135514304#!/compare/1535414400/1546041600

https://backpack.tf/item/4842921415

History on the tickets don’t match because the seller sold the tickets to bots before they were scanned in their backpack. You can see metal coming from the bot the tickets went to.

X = 9.5

Marketplace sales:

Sold for $17.79

https://marketplace.tf/items/1162;5;u3009

https://manic.tf/keyprice/?at=2019-01-01 - $17.79 / $1.76 = 10.11 keys

X = 10

Other Sales:

https://backpack.tf/item/6058737879 (#1)

https://backpack.tf/item/5051597217 (#2)

https://backpack.tf/item/5046833437 (#3 & #4)

#1

Untraceable

https://backpack.tf/profiles/76561198085685000#!/compare/1547683200/1548201600

https://backpack.tf/profiles/76561198363395191#!/compare/1548115200/1548201600

#2

Transferred to bot account

https://backpack.tf/profiles/76561198090737788#!/compare/1547942400/1548288000

https://backpack.tf/profiles/76561198311725787#!/compare/1548115200/1548288000

#3

SCM

https://backpack.tf/profiles/76561198373719952#!/compare/1546214400/1546300800

https://backpack.tf/profiles/76561198122774608#!/compare/1544054400/1546560000

#4

Untraceable

https://backpack.tf/profiles/76561198122774608#!/compare/1547424000/1547510400

https://backpack.tf/profiles/76561198290285205#!/compare/1547683200/1548460800

Sellers:

https://i.imgur.com/5RoKNHf.png

https://backpack.tf/item/6058737879 - 11 keys

https://backpack.tf/item/5051597217 - 12 keys

https://backpack.tf/item/5421943353 - 14 keys

https://backpack.tf/item/6786014099 - 16 keys

Sales at:

9.5

10

13

13 is too high given current sellers. Excluding 13.

Going with 9.5-10.