Update!

Sale: https://marketplace.tf/items/tf2/30763;5;u3019 - 33/2 = ~17

https://backpack.tf/item/6074749581

Rest of the mp.tf sales:

33/1.92 = ~17

20/1.89 = ~11

Additional by Xergoyf:

seems to of sold for 8 keys here (outdated technically tho) took ~1 month to sell

https://backpack.tf/profiles/76561198358296372#!/compare/1592784000/1592870400

https://backpack.tf/item/4989654153

Also $14.5 / $1.98 = 7.32 keys while we are looking at slightly outdated sales. These sales were within a month of the 17 sales

https://imgur.com/a/TZyy98q

https://backpack.tf/item/4962602206

https://backpack.tf/profiles/76561198358296372#!/compare/1594504800/1594591200

Sold for 10 keys, dumped on 7.5 buy order then sold for 10 again

https://backpack.tf/item/4962602206 - 2nd mp sale was prob from person who bought from pauling. Brain_Soup doesn't own anymore, so maybe dumped for the 11 key mp sale? So 17 sold for 11.

So basically sales at:

7.5 (x2)

8

10 (x2)

11

17 (x2)

10 - 11 should be best here.

10-11 it is!