Sale 1:

Sold for $19 on Marketplace.tf

https://marketplace.tf/items/30844;5;u3008

Can’t find item’s history

19/1.97 = ~9.64

X = 9.5

Sale 2:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198322876605#!/compare/1523059200/1523145600

Buyer: https://backpack.tf/profiles/76561198340621517#!/compare/1523059200/1523145600

X = 6

Sale 3:

Sold for 4 keys + minor amount in items

Seller: https://backpack.tf/profiles/76561198007146188#!/compare/1523059200/1523836800

Buyer: https://backpack.tf/profiles/76561198066584736#!/compare/1523750400/1523836800

X = 4

Sellers:

~5.65 keys:

https://i.imgur.com/lwH4yvw.png

~5.73 keys:

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

https://backpack.tf/item/6266535928

https://backpack.tf/item/6360702246

10 keys:

https://i.imgur.com/LO57uI5.png

https://backpack.tf/item/6446858991

Sales at:

4

6

9.5

9.5 is an outlier, given all the cheaper sellers. Excluding 9.5

https://i.imgur.com/UQ9jqKz.png - Buyers at 5+ keys, excluding 4.

Several for sale at ~5.5 keys, using that as the low-end.

Going with 5.5-6.