Item 1

https://backpack.tf/item/15342759098

Sale 1

https://backpack.tf/profiles/76561198040409248#!/compare/1757635200/1760227200

https://backpack.tf/profiles/76561199111073161#!/compare/1759276800/1759363200

No clue, only an incomplete amount matches

Sale 2

https://gyazo.com/c6cf4a33aa0c4ed6ea185f43ed11cda3

https://backpack.tf/profiles/76561199111073161#!/compare/1759536000/1759622400

https://backpack.tf/profiles/76561198170165054#!/compare/1759536000/1759622400

13 keys (16244961091) => Matches the B/O perfectly

Item 2

https://backpack.tf/item/13676376937

Sale 3

https://backpack.tf/profiles/76561199226727353#!/compare/1753056000/1753401600

https://backpack.tf/profiles/76561199084784906#!/compare/1752969600/1753056000

No clue

Sale 4

https://backpack.tf/profiles/76561199110809353#!/compare/1757116800/1757203200

https://backpack.tf/profiles/76561198090616117#!/compare/1756166400/1757203200

13 keys

Item 3

https://backpack.tf/item/7682267273

Sale 5

https://backpack.tf/profiles/76561197996906196#!/compare/1755129600/1755648000

https://backpack.tf/profiles/76561199059698603#!/compare/1755388800/1755475200

Dumped for an unknown amount

Sale 6

https://backpack.tf/profiles/76561199084784906#!/compare/1755907200/1755993600

https://backpack.tf/profiles/76561198128882492#!/compare/1755907200/1755993600

Only 6 keys trace, incomplete

Item 4

https://backpack.tf/item/15547726631

Sale 7

https://backpack.tf/profiles/76561199059698603#!/compare/1753920000/1754006400

https://backpack.tf/profiles/76561198311498888#!/compare/1757635200/1757721600

No clue

Sale 8

https://marketplace.tf/items/tf2/30375;5;u6

$29.99 / $1.90 = ~16 keys (Sep 29)

Total Sales

13, 13, 16

https://gyazo.com/d82072bbfabeb249a656a4cbd3b8338f

20 --> 13 is a bit of a steep drop

I'll go with 13 - 16 keys since the median is where the current lowest is anyways...

Unsolds:

https://backpack.tf/item/13676376937 - ~14.5

https://backpack.tf/item/15182157553 - $79.99