Sale 1:

Sold for $26.4 on Marketplace.tf

https://marketplace.tf/items/174;5;u36

https://backpack.tf/item/972971366

26.4/1.95 = ~13.54

Going to round down, because normally, I would exclude a sale like this when there are multiple sellers for cheaper, but there are no sales at what the sellers are selling at. (I also can’t tell what the exact price of keys was this day, so I used an estimate.)

X = 13

Sale 2:

Sold for Cloud 9 Steel Shako (12) + ~1 key in items

No outpost

Seller: https://backpack.tf/profiles/76561198098812857#!/compare/1504915200/1505001600

Buyer: https://backpack.tf/profiles/76561198019894955#!/compare/1504915200/1505606400

X = 13

Sale 3:

Bulk for Logo Private Eye

Seller: https://backpack.tf/profiles/76561198137012610#!/compare/1504483200/1505001600

Buyer: https://backpack.tf/profiles/76561198188251237#!/compare/1504915200/1505001600

Sellers:

11 keys:

https://i.imgur.com/ok8B7rg.png - 3 days

https://i.imgur.com/JmfwGDh.png - 1 day

12 keys:

https://i.imgur.com/K8FVQTz.jpg - 3 days

https://i.imgur.com/IIUBb1H.png - 26 days

Offers:

http://www.tf2outpost.com/trade/29375220 - 2 weeks

Sales at:

13 (2x)

Sellers at 11 and 12.

Going with 11-13.