Item 1: https://backpack.tf/item/16149918121

Sale 1: Untrace

https://backpack.tf/profiles/76561198157634038#!/compare/1757980800/1758067200

https://backpack.tf/profiles/76561198998524346#!/compare/1757980800/1758067200

Sale 2: Incomplete, 2 keys outgoing from buyer link, but nothing else outgoing does, nor does seller have anything incoming from buyer

https://backpack.tf/profiles/76561198998524346#!/compare/1758672000/1758758400

https://backpack.tf/profiles/76561198112959245#!/compare/1758412800/1758758400

Item 2: https://backpack.tf/item/7957381029

Sale 1: 19k pure, you can see Mogyi dumps an Orbiting Fire Head Warmer and receives some keys, these 3 keys are from Unusual #2, who is the same provider of the 19k bundle that is received by the seller

https://backpack.tf/profiles/76561199193412191#!/compare/1757030400/1757116800

https://backpack.tf/profiles/76561198156734725#!/compare/1757030400/1757203200

Item 3: https://backpack.tf/item/6454865660

Sale 1: Untrace

https://backpack.tf/profiles/76561199026390261#!/compare/1755907200/1755993600

https://backpack.tf/profiles/76561199764032554#!/compare/1755734400/1755993600

Sale 2: Presumably the marketplace sale on Sept 16th, as it moves right after

Sale 3: Bot dump, seller's side outdated

https://backpack.tf/profiles/76561198801206583#!/compare/1757808000/1758412800

https://backpack.tf/profiles/76561199186541168#!/compare/1758412800/1758499200

Item 4: https://backpack.tf/item/6218137902

Sale 1: Untrace from seller's side, looks like bulk on buyer's side

https://backpack.tf/profiles/76561199014000737#!/compare/1759104000/1759536000

https://backpack.tf/profiles/76561198139627699#!/compare/1759190400/1759276800

Sale 2: Bulk

https://backpack.tf/profiles/76561198139627699#!/compare/1759536000/1759622400

https://backpack.tf/profiles/76561198070774923#!/compare/1759536000/1759622400

Sale 3: Untrace

https://backpack.tf/profiles/76561198882175555#!/compare/1759708800/1759795200

https://backpack.tf/profiles/76561198070774923#!/compare/1759708800/1759795200

Marketplace sale:

https://marketplace.tf/items/tf2/30038;5;u61

Sold for $39.99 Sept 16th

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

Key price for the day is $1.84

$39.99 / $1.84 = 21.73k

Classifieds link: https://imgur.com/a/SikoEEm

Sales at 19k and 21.73k, after rounding up the marketplace sale to 22 keys it feels a bit high with unsolds at 23 keys for an entire month, but given how close it is to 19 keys, I'd keep this in the range for now.

Taking 19k for the low end and 22k for the high end.