First sugg yeah !

Sale #1 :

https://backpack.tf/profiles/76561198075684088#!/compare/1503878400/1503964800

https://backpack.tf/profiles/76561198095862827#!/compare/1503878400/1503964800

Sold for 80 pure

x = 80

Sale #2 :

https://backpack.tf/profiles/76561198012599344#!/compare/1509062400/1509148800

https://backpack.tf/profiles/76561198096896377#!/compare/1509062400/1509148800

I can't get this one

Sale #3 :

https://backpack.tf/profiles/76561198160856661#!/compare/1509235200/1509321600

https://backpack.tf/profiles/76561198096896377#!/compare/1509235200/1509321600

Sold with a Pro KS Aussie Grenade Launcher (18) for a Power Surge Slo-Poke, better use this sale on the Poke

Sale #4

https://backpack.tf/profiles/76561198208814695#!/compare/1509321600/1509408000

https://backpack.tf/profiles/76561198160856661#!/compare/1509321600/1509408000

Sold for a Fountain of Delight Taunt: The High Five! (110, lowest seller at 85) + a Smoking Salty Dog (34.5)

x = 85 + 34.5 ~120 (better need minis on both of these, but this sale may remain an outlier)

Sale #5:

https://backpack.tf/profiles/76561198208814695#!/compare/1509667200/1509753600

https://backpack.tf/profiles/76561198079413347#!/compare/1509667200/1509840000

Quickbought for 60 keys pure via buy order

x = 5

Sale #6 :

https://backpack.tf/profiles/76561198095862827#!/compare/1509667200/1509840000

https://backpack.tf/profiles/76561198059011775#!/compare/1509580800/1509840000

Sold with a Strange Killstreak Festive Rocket Launcher (10) and a Green Confetti Thirst Blood (16.5) for a Scorching Flames Archer's Sterling (105).

10 + 16.5 + x = 105 => x = 78.5 rounding to 79

x = 79

I think that's all the sales that happened. I've been following this item for a while now but I don't have premium so correct me if i'm wrong :)

Sales : 60 (qs), 79, 80, 120 (outlier)

Gonna go for 79-80

Thanks for reading this far, let me know your feedback.

New sale ;

https://backpack.tf/profiles/76561198217898749#!/compare/1510099200/1510272000

Sold with ~30 keys in items for a PE Compagny Man priced 7 months ago at 106 keys

New sale : https://backpack.tf/item/5224967888

Sold with 6 keys in sweet for a KaW Cone (56) + Terror Watt Company Man (28)

X+6 = 56 + 28 => 78 keys

New sales :

Sale #9 :

https://backpack.tf/profiles/76561198134266699#!/compare/1511049600/1511136000

Sold with a Purple Energy Swagman's Swatter (70 in date) for a Bonzo The All-Gnawing Tartan Tyrolean (suggestion at 138) + 10 keys

70 + x = 138 + 10 => x = 78

Sale #10 :

https://backpack.tf/profiles/76561198338343295#!/compare/1511395200/1511481600

https://backpack.tf/profiles/76561198160856661#!/compare/1511395200/1511481600 (here we can see the number of keys added)

Sold for a Tesla Coil Noble Nickel Amassment of Hats (35) + Voltaic Hat Protector Universal Translator (22) + 20 keys pure

x = 77

Better resuggest at 77-80 ?