Not bad.

Sale 1, 2, 3 & 4: Marketplace

https://marketplace.tf/items/tf2/611;5;u57

https://backpack.tf/item/2204753043

https://backpack.tf/item/1733999140

22.17 on April 4, 2020 (22.17/1.72 = 12.88 rounding to 13 keys)

56.99 on April 21, 2020 (56.99/1.79 = 31.83 rounding to 32 keys)

43.95 on May 14, 2020 (43.95/1.9 = 23.13 rounding to 23 keys)

44.99 on May 15, 2020 (44.99/1.91 = 23.55 rounding to 24 keys)

Sale 5: Bulk

https://backpack.tf/profiles/76561198975565852#!/compare/1589328000/1589414400

https://backpack.tf/profiles/76561198189381361#!/compare/1589328000/1589500800

Sale 6: Unknown, one of the sales from marketplace maybe?

https://backpack.tf/profiles/76561198975565852#!/compare/1589414400/1589500800

https://backpack.tf/profiles/76561198177872379#!/compare/1589328000/1589414400

Sale 7: Unknown

https://backpack.tf/profiles/76561198185579770#!/compare/1589068800/1589241600

https://backpack.tf/profiles/76561198189381361#!/compare/1589068800/1589155200

Sale 8: Unknown

https://backpack.tf/profiles/76561198176022675#!/compare/1585872000/1586044800

https://backpack.tf/profiles/76561198043936328#!/compare/1585872000/1586044800

Sale 9: Unknown

https://backpack.tf/profiles/76561198402039752#!/compare/1585872000/1585958400

https://backpack.tf/profiles/76561198176022675#!/compare/1585872000/1585958400

Sale 10: Sold with 1 key for?

https://backpack.tf/profiles/76561198275012706#!/compare/1585440000/1585526400

https://backpack.tf/profiles/76561198402039752#!/compare/1585353600/1585440000

Classifieds:

https://gyazo.com/9f4143d65a3b8bb6d807d22496209aba

Sales at 13, 23, 24, and 32. There are buyers at 16+. There are sellers at 29 and 30. Excluding 13 and 32. Taking a range of 23-24 keys here.