Using last 30 days

Sales 1 & 2:

Sold for $13.85 and $13.89 on Marketplace.tf

https://marketplace.tf/items/30673;5;u3009

13.89/1.99 = ~6.98

13.85/1.97 = ~7.03

X = 7 (2x)

Sale 3:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198092382473#!/compare/1523577600/1523664000

Buyer: https://backpack.tf/profiles/76561198331624030#!/compare/1523577600/1523664000

X = 5

Sale 4:

Sold with some crates and keys for a lot of items

Seller: https://backpack.tf/profiles/76561197993931314#!/compare/1523664000/1523923200

Buyer: https://backpack.tf/profiles/76561198402730531#!/compare/1511481600/1523664000

This sale’s too dumb to be used.

Sale 5:

Bulk for FoD Burstchester

Seller: https://backpack.tf/profiles/76561198402730531#!/compare/1523664000/1523750400

Buyer: https://backpack.tf/profiles/76561198055622215#!/compare/1523664000/1523750400

Sale 6:

Bulk for keys

Seller: https://backpack.tf/profiles/76561198259342040#!/compare/1523404800/1523491200

Buyer: https://backpack.tf/profiles/76561198085004062#!/compare/1523404800/1523491200

Mega strike Fubar was involved.

Sellers:

~9.55 keys:

https://i.imgur.com/h2uhU90.png

https://backpack.tf/item/4899450839

10 keys:

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

https://backpack.tf/item/4951622880

https://marketplace.tf/items/30673;5;u3009 – Listed for ~7 keys worth on Marketplace.tf

https://i.imgur.com/Tl7jFGl.png

https://backpack.tf/item/6481470087

https://i.imgur.com/z0rSUZv.png

https://backpack.tf/item/5386672890

Offers:

http://www.tf2outpost.com/trade/29600624

SCM: (Only including important ones)

https://i.imgur.com/Gw8KRPD.png

$13.49 (~5.46 keys)

$13.51 (~5.47 keys)

$16.90 (~6.84 keys)

$17.25 (~6.98 keys)

$19.86 (~8.04 keys)

Sales at:

5

7 (2x)

Going with 5-7.