From existing items there are only 2 with history.

Sale 1 (08 Aug 2022) - 114 keys:

History: https://backpack.tf/item/7956348410

Compare 1 (F4tJoe): https://backpack.tf/profiles/76561198255764866#!/compare/1659830400/1659916800

Removed:

Purple Energy Larrikin Robin - 38 keys

Green Energy Hat of Cards - x

Obtained:

152 keys

x = 152 - 38 = 114 keys

Compare 2 (akk0): https://backpack.tf/profiles/76561198042479716#!/compare/1659916800/1660176000

Removed:

251 keys

lowtier items - 1 key

Obtained:

Strange Professional Killstreak Australium Knife - 33 keys

Strange Professional Killstreak Australium Sniper Rifle - 63 keys

lowtier items - 3 keys

Purple Energy Larrikin Robin - 38 keys

Green Energy Hat of Cards - x

x = 251 + 1 - 33 - 63 - 3 - 38 = 115

So we can safely say Green Energy Hat of Cards sold for 114 keys with proof on both sides.

Stats for Purple Energy Larrikin Robin at the time of sale:

https://gladiator.tf/time-machine?item=Purple+Energy+Larrikin+Robin&at=2022-08-08T21%3A43%3A00.000Z

https://backpack.tf/vote?quality=5&item=Larrikin+Robin&priceindex=10&tradable=1&craftable=1&state=0%2C1%2C2&unvotable=1&australium=-1&killstreak_tier=0&elevated=-1&sort=popular

Buyers: 35 keys

Suggestion: 30 keys

Lowest seller: 48 keys

I will count it as average of these 3, that is around 38 keys because its highly probable they did the same

agreeing to finalize trade.

Sale 2 (excluded as quicksale):

https://backpack.tf/item/3953395006

Compare 1 (lemonJUICE): https://backpack.tf/profiles/76561198157279796#!/compare/1658188800/1658275200

Removed:

Green Energy Hat of Cards - x

Abyssal Aura Racc Mann - 66 keys

Strange Professional Killstreak AWPer Hand - 35 keys

Max's Severed Head - 28 keys

Obtained:

201 keys

x = 201 - 66 - 35 - 28 = 72 keys

Compare 2 (Oli B>QS/BP/Bulk w/ 1.2k+ keys): https://backpack.tf/profiles/76561198140316312#!/compare/1658188800/1658275200

Stats for Abyssal Aura Racc Mann at the time of sale:

https://gladiator.tf/time-machine?item=Abyssal+Aura+Racc+Mann&at=2022-07-19T18%3A14%3A00.000Z

https://backpack.tf/vote?quality=5&item=Racc+Mann&priceindex=125&tradable=1&craftable=1&state=0%2C1%2C2&unvotable=1&australium=-1&killstreak_tier=0&elevated=-1&sort=popular

Buyers: 66 keys

Suggestion: 85 keys

Lowest seller: 85 keys

Since buyer is a well known quickbuyer and there was a seller at 85, data suggests they counted the hat as pure as buy orders

so Im taking it as 66 keys.

Looks like the hat got quicksold to known quickbuyer at 2 keys over at the time buy orders. So I exclude it as quicksale.

Sale 3 (looks like was a gift so no sale):

https://backpack.tf/profiles/76561198011707565#!/compare/1658102400/1658188800

Kazuki, ScienceDILF gave it away for free with some other items to lemonJUICE on the same they that latter sold it. Possily just alt account.

Rest of trades happened day after day so all was either 'gifts' or quickselling.

Sale 3 (untractable):

https://backpack.tf/profiles/76561198311322510?time=1657600569

Sale 4 (transfer from banned account to alt (probably)).

I take 114 keys flat.