Item 1

https://backpack.tf/item/13671136435

Sale 1

https://backpack.tf/profiles/76561199564942025#!/compare/1720656000/1720569600

https://backpack.tf/profiles/76561198105321885#!/compare/1720656000/1720742400

18 keys + the ref on buyer side match = ~19 keys

Item 2

https://backpack.tf/item/13656011040

Skipping past mannco.store...

Sale 2

https://backpack.tf/profiles/76561198050959046#!/compare/1724976000/1725062400

https://backpack.tf/profiles/76561199746241974#!/compare/1724976000/1725062400

Bulk for a North Star Blast Defense

Sale 3

https://backpack.tf/profiles/76561199746241974#!/compare/1725062400/1725148800

https://backpack.tf/profiles/76561199033547170#!/compare/1725148800/1725235200

15 keys, 20 ref = ~15 keys

Sale 4

https://backpack.tf/profiles/76561199033547170#!/compare/1725235200/1725321600

https://backpack.tf/profiles/76561198410895925#!/compare/1724371200/1725235200

Might be a missing history, but it looks like it was bought for 18 keys

Item 3

https://backpack.tf/item/13709950572

(Mp sale will be covered below...)

Sale 5

https://backpack.tf/profiles/76561198161416190#!/compare/1722384000/1723161600

https://backpack.tf/profiles/76561199245017571#!/compare/1677801600/1725840000

Seller inv is private

Item 4

https://backpack.tf/item/13646786325

Sale 6

https://backpack.tf/profiles/76561198981913112#!/compare/1723939200/1724112000

https://backpack.tf/profiles/76561198271577665#!/compare/1724025600/1724112000

Bulk for a Stellar Ascent Mean Captain

Sale 7

https://backpack.tf/profiles/76561198271577665#!/compare/1726531200/1726617600

https://backpack.tf/profiles/76561198056885233#!/compare/1726617600/1726876800

Looks like 20 keys

Mp.tf

https://marketplace.tf/items/tf2/31391;5;u300

https://backpack.tf/item/13661185572

$39.95 / $1.69 = ~24 keys (Jul 10)

$39.95 / $1.74 = ~23 keys (Aug 3)

$39.95 / $1.81 = ~22 keys (Aug 14)

$39.95 / $1.89 = ~21 keys (Sep 16)

$39.95 / $1.88 = ~21 keys (Sep 18)

Total Sales

15, 18, 19, 20, 21, 21, 22, 23, 24

https://imgur.com/a/lsPaSmv

15 seems a little low given other sales

20 took nearly a month to sell

I'll use that as the middle point and avg it out with 18 - 22 keys? c: (Those are the more recent sales anyways...)