"Price will probably be adjusted soon anyways" - https://backpack.tf/suggestion/50982352ba25366d30000000

Resuggestion: https://backpack.tf/suggestion/5fd0884d1a9c0c6aa43b3c42

1 of 1 with one recent sale: https://backpack.tf/item/1228627582

The Sale:

https://backpack.tf/profiles/76561198066896831#!/compare/1606176000/1606262400

https://backpack.tf/profiles/76561197966756586#!/compare/1606176000/1606262400

Sold for Burning Flames Salty Dog + The Ooze Brigade Helm + It's A Secret To Everybody Attendant + 104 keys.

Putting mini prices here for simplicity:

Burning Flames Salty Dog: 215

The Ooze Brigade Helm: 104

It's A Secret To Everybody Attendant: 225

Mini for Burning Flames Salty Dog:

https://backpack.tf/item/7742897376 - only item with recent history except for the one seen in this trade (which doesn't have any usable sales).

Sale 1:

https://backpack.tf/item/7742897376

https://backpack.tf/profiles/76561198063640894#!/compare/1601510400/1601856000

https://backpack.tf/profiles/76561198061164674#!/compare/1601510400/1602028800

Either untraceable or bulk for a Burning Flames Brotherhood of Arms that is never indexed inside the seller's inventory, which is highly unlikely.

Sale 2:

https://backpack.tf/item/7742897376

https://backpack.tf/profiles/76561198061164674#!/compare/1606176000/1606521600

https://backpack.tf/profiles/76561198188093413#!/compare/1606435200/1606521600

Entirely untraceable. Sits in the seller's inventory marked as "changed" for a month, and then disappears. I am unable to find the date on which it enters the buyer's inventory, either.

These are the only two usable sales. The other item with recent history, https://backpack.tf/item/5367090858, only sees this trade and a short-lived borrowing/brokering between ZeMajestic and gsdgsdgs. I, we can take the value to be the current backpack.tf price of 215 keys.

Mini for The Ooze Brigade Helm:

https://backpack.tf/suggestion/5fd06b4a4f92e6120828ceab

104 keys.

Mini for It's A Secret To Everybody Attendant:

https://backpack.tf/suggestion/5fd07c70ca6e124bbc62c3cb

225 keys.

Conclusion:

215+225+104+104=648 keys, rounding to 650.

Capping at 500 per Wayne's B/O: https://i.imgur.com/natlxY5.png (credit to Payback for the screenshot)