This one looks fun.

Sale 1: Sold for 13 keys

https://backpack.tf/profiles/76561198411392321#!/compare/1589846400/1590192000

https://backpack.tf/profiles/76561198172690987#!/compare/1589760000/1589846400

Sale 2: Bulk for Pyroland Daydream Racc Mann

https://backpack.tf/profiles/76561198045883624#!/compare/1583798400/1585267200

https://backpack.tf/profiles/76561198125791160#!/compare/1584835200/1584921600

Sale 3: Unknown

https://backpack.tf/profiles/76561198985924682#!/compare/1586044800/1586131200

https://backpack.tf/profiles/76561198047743975#!/compare/1586044800/1586131200

Sale 4, 5, 6, 7 & 8: Marketplace

https://marketplace.tf/items/tf2/31058;5;u124

https://backpack.tf/item/8188032335

https://backpack.tf/item/8175440503

41 on March 31, 2020 (41/1.69 = 24.26 rounding to 24 keys)

40.01 on April 3, 2020 (40.01/1.7 = 23.5 rounding to 24 keys)

35.99 on May 3, 2020 (35.99/1.87 = 19.24 rounding to 19 keys)

35.99 on May 12, 2020 (35.99/1.9 = 18.94 rounding to 19 keys)

35.99 on May 16, 2020 (35.99/1.89 = 19.04 rounding to 19 keys)

Sale 9: Unknown

https://backpack.tf/profiles/76561198301887399#!/compare/1587859200/1587945600

https://backpack.tf/profiles/76561198002757046#!/compare/1587859200/1587772800

Sale 10: Unknown

https://backpack.tf/profiles/76561198415479324#!/compare/1585094400/1585440000

https://backpack.tf/profiles/76561198418566428#!/compare/1584921600/1585353600

Classifieds:

https://gyazo.com/069707a40a86a21bb10239ae97c2aee0

Sales at 13, 19, 19, 19, 24, and 24. Current classifieds have sellers from 17-18. Excluding 24. Taking a range of 13-19 keys here.