Sale 1:

Sold for Stormy Wraith (Suggestion at 33) + 4 keys

No outpost

Seller: https://backpack.tf/profiles/76561198050114720#!/compare/1510876800/1510963200

Buyer: https://backpack.tf/profiles/76561198059800108#!/compare/1510963200/1511049600

X = 37

Sale 2: (Dupe)

Sold for $70 on Marketplace.tf

https://marketplace.tf/items/611;5;u65

https://backpack.tf/item/1772121403

70/1.9 = ~36.8

X = 37

Sale 2:

Sold for Bubbling Rotation (Suggestion at 28) + 3 keys

No outpost

Seller: https://backpack.tf/profiles/76561198112660684#!/compare/1510531200/1510704000

Buyer: https://backpack.tf/profiles/76561198263995096#!/compare/1510617600/1510704000

X = 31

Sale 3:

Sold for 30 keys

No outpost

Seller: https://backpack.tf/profiles/76561198090869623#!/compare/1509926400/1510012800

Buyer: https://backpack.tf/profiles/76561198147530243#!/compare/1509840000/1510012800

X = 30

Sale 4:

Sold with 5 keys for Green Energy Towering Titanium

No outpost

Seller: https://backpack.tf/profiles/76561198263995096#!/compare/1510876800/1510963200

Buyer: https://backpack.tf/profiles/76561198050114720#!/compare/1510876800/1510963200

Can be used on the titanium.

Sale 5:

Bulk for Screaming Tiger Conga

Seller: https://backpack.tf/profiles/76561198210372209#!/compare/1507420800/1507507200

Buyer: https://backpack.tf/profiles/76561198090869623#!/compare/1507420800/1507507200

Bubbling Rotation:

https://backpack.tf/suggestion/5a27a66544325a30b0445933

Sellers:

40 keys:

https://i.imgur.com/U85IS6S.png - 2 days

Sales at:

30

31

37 (2x, 1 dupe)

Going with 30-37.