Now with even more proof thanks to Shuffle Spy !

Bought it on Marketplace for 540$

https://marketplace.tf/items/tf2/30175;5;u38;kt-2

Median price for keys was at 1.82$

https://marketplace.tf/items/tf2/5021;6

540$ / 1.82$ = 296.7 Keys

Rounding to 297

Sale 2

Sold 1:1 for a Burning Flames Brotherhood of Arms

https://backpack.tf/profiles/76561198144628116#!/compare/1579996800/1585612800

https://backpack.tf/profiles/76561197993888396#!/compare/1585440000/1585612800

https://backpack.tf/item/5389366554

Brotherhood sales:

https://backpack.tf/profiles/76561198057412106#!/compare/1585872000/1585958400 - Scorching Flames Peak + Beams Cotton + Cloudy Moon AA

https://imgur.com/a/nlIDYfJ - The Peak/Cotton/AA sale is capped by the buyout of 349 Keys

https://backpack.tf/profiles/76561197989031107#!/compare/1586995200/1587168000 - Ethereal Peak (130) + Beams Nuke (82.5) + Snowfallen Trucker (55)

https://backpack.tf/profiles/76561198118922746#!/compare/1584835200/1584921600 - There was a Max's added to the sale you used

https://marketplace.tf/items/tf2/30066;5;u13 + https://backpack.tf/item/5389366554 - Sold for $475 (250 Keys)

https://backpack.tf/profiles/76561198044111092#!/compare/1588982400/1589068800 - ?

https://backpack.tf/profiles/76561198118130177#!/compare/1584576000/1585094400 - ?

Using ~300 for the Brotherhood

Ethereal Peak sales:

https://backpack.tf/profiles/76561198058569038#!/compare/1582156800/1582243200 - Icefall Cane (84 Keys) + Sparkling Cane (60.5 Keys)

https://backpack.tf/profiles/76561197964171516#!/compare/1582243200/1582329600 - 125 Keys

Rifleman sales:

https://backpack.tf/profiles/76561198090448861#!/compare/1587945600/1588204800 - 140 Keys

https://backpack.tf/profiles/76561198079634422#!/compare/1583193600/1583280000 - Haunted Ghosts Yellow Belt + Green Energy Scotch Bonnet

https://backpack.tf/profiles/76561198114402400#!/compare/1583193600/1583280000 - Nebula Universal Translator + 30 Keys + Sweets

https://imgur.com/a/SEKW1W4 - The Translator sale is capped by the buyout of 345 Keys

https://backpack.tf/profiles/76561198118922746#!/compare/1586131200/1586217600 - Better for the Executioner

https://backpack.tf/profiles/76561198134238543#!/compare/1586736000/1586822400 - Approximately 140 Keys

https://backpack.tf/profiles/76561197961420647#!/compare/1586822400/1586908800 - Approximately 125 Keys

Using ~140 for the Rifleman

With the Marketplace sale and the item trades being very close to 300 keys each I am going to use 300 keys flat for the suggestion now.