Sale 3 wouldn't be a bulk sale. Using 255 for the Blast Defense (that suggestion was made a before the HKC sale), sale 3 would be 767 Keys. It and the other sales here are too old now, so that's a moot point.

https://backpack.tf/profiles/76561198111108219#!/compare/1743033600/1743206400 - Being used for the Hellmet

https://backpack.tf/profiles/76561198850407517#!/compare/1743984000/1744156800 - Added the Spectral Fire Blast Defense (207 Keys) for a Burning Flames Mining Light + 10 Keys

https://imgur.com/a/JKAZsRk - The Mining sold for 750 Keys + Orbiting Planets Brainiac Hairpiece (225 or 225 - 240)

750 + 225 + 10 - 207 = 778 Keys, and if the Brainiac is 225 - 240, then 750 + 232.5 + 10 - 207 = 785.5 Keys. Rounding to 780 to be safe would be fine.

Brainiac sales:

https://backpack.tf/profiles/76561198337378097#!/compare/1744416000/1744502400 - Added a Phosphorous Cloud Crasher (117.5 Keys) for a Blizzardy Pencil + Smoking Whirly (80 Keys) + Tangled Roasty Toasty (~6 Keys)

https://backpack.tf/profiles/76561198157964204#!/compare/1746662400/1746835200 - No Mini for the Tyrant's

https://backpack.tf/profiles/76561198157710101#!/compare/1742342400/1742428800 - Twisted Radiance Field Practice (110) + Twisted Radiance Brass Bucket (buyers at 62, no sales) + Twisted Radiance Airdog (49) + Warp Drive Frigid Fashion (40) = high with current sellers at 245

https://backpack.tf/profiles/76561197966756586#!/compare/1743811200/1743984000 - Added 35 Keys for a Roboactive Modest Metal Pile of Scrap

https://imgur.com/a/tlKu08u - The Modest has sellers at $500 (~259 Keys), so the Brainiac would be 224 Keys

If the Mostacho mini for the Pencil can be proven to be 105, then 225 - 240 would work as a range for the Brainiac

Pencil sales:

https://backpack.tf/profiles/76561198055622215#!/compare/1743379200/1743552000 - Ominous Mostacho (105?) + Mallard Beret (75) + Mallard Buddy (53) + Mallard Bone Dome (50)

https://backpack.tf/profiles/76561198009093543#!/compare/1742947200/1743033600 - The Mostacho might've sold for 105 Keys, 34 from the Kit

https://backpack.tf/profiles/76561198055622215#!/compare/1743552000/1743638400 - The Beret has a sale for 75

https://backpack.tf/profiles/76561198311498888#!/compare/1743465600/1743552000 - The Buddy's only sale is 52 Keys + ~1 Key of Refined

https://backpack.tf/profiles/76561199026390261#!/compare/1743465600/1743552000 - The Bone Done's only sale is 49 Keys + ~1 Key of Refined

https://backpack.tf/profiles/76561198063640894#!/compare/1740614400/1740700800 - VfB MN Pyromancer's + 241 Keys + 2x Spelled Strange Degreaser (57.5 Keys)

https://backpack.tf/profiles/76561198833734475#!/compare/1740614400/1740700800 - The Degreaser sold for a Strange Pro KS Shooting Star

https://gladiator.tf/sales?item=Strange%20Professional%20Killstreak%20Shooting%20Star&at=2025-03-24T15:51:52.744Z - Shooting Star sales ~55 - 60

https://backpack.tf/profiles/76561198340999409#!/compare/1738713600/1738800000 - The Degreaser also sold for 57 Keys

The Pyromancer's only has a sale from December. If we're to use the two HKC sales from my comment as the recent ones in place of the sales in the suggestion, that means the Pyromancer's has no usable mini, so 780 flat would work. The suggested price is close enough.

also just to expand on this, the 850 was already accepted and still is in-date of this suggestion.