History 1: https://backpack.tf/item/9271463807

Only a key matches:

https://backpack.tf/profiles/76561198188093413#!/compare/1614470400/1614556800

https://backpack.tf/profiles/76561197978439752#!/compare/1614384000/1614470400

History 2: https://backpack.tf/item/9256782524

Mannco.Store sale https://mannco.store/item/23251

April 1: $54.86/1.93=28.42 ~28 keys

Untraceable:

https://backpack.tf/profiles/76561198082864462#!/compare/1617235200/1617321600

https://backpack.tf/profiles/76561199149146362#!/compare/1616976000/1617408000

30 keys match in buyer's compare:

https://backpack.tf/profiles/76561199149146362#!/compare/1617408000/1617494400

https://backpack.tf/profiles/76561198035897364#!/compare/1617408000/1617494400

History 3: https://backpack.tf/item/9234565767

Untraceable:

https://backpack.tf/profiles/76561198277994453#!/compare/1610755200/1612569600

https://backpack.tf/profiles/76561198011827547#!/compare/1612483200/1612569600

History 4: https://backpack.tf/item/9209716741

Looks like brokering

History 5: https://backpack.tf/item/9201124773

Tradeback

History 6: https://backpack.tf/item/9198852024

Sold on Mannco.Store: https://mannco.store/item/23251

April 2: $66.66/1.92=34.72 ~35 keys

History 7: https://backpack.tf/item/9196841160

Sold to a quickbuyer:

https://backpack.tf/profiles/76561198019000176#!/compare/1615334400/1615766400

https://backpack.tf/profiles/76561198841279602#!/compare/1615680000/1615766400

Sold for 34 keys:

https://backpack.tf/profiles/76561198841279602#!/compare/1617580800/1617667200

https://backpack.tf/profiles/76561198131452826#!/compare/1617235200/1619049600

History 8: https://backpack.tf/item/9164670251

Sold to a bot:

https://backpack.tf/profiles/76561198347573909#!/compare/1612310400/1612483200

https://backpack.tf/profiles/76561199102237820#!/compare/1612310400/1612396800

Untraceable/Sold within a day:

https://backpack.tf/profiles/76561199102237820#!/compare/1612742400/1612828800

https://backpack.tf/profiles/76561199078477600#!/compare/1612396800/1612828800

Dumped to a quickbuyer:

https://backpack.tf/profiles/76561199078477600#!/compare/1612828800/1612915200

https://backpack.tf/profiles/76561198841279602#!/compare/1612742400/1612828800

Sold on Marketplace.tf: https://marketplace.tf/items/tf2/31115;5;u155

February 13: $79.99/2.13=37.55 ~38 keys

History 9: https://backpack.tf/item/9156560477

Searing Plasma Blast Defense + Fountain of Delight Taunt: Buy A Life + Skill Gotten Gains Taunt: Spent Well Spirits + Fountain of Delight Taunt: I See You + 4 Crate #83's + 2 keys:

https://backpack.tf/profiles/76561197994697258#!/compare/1615075200/1615161600

https://backpack.tf/profiles/76561198071784409#!/compare/1615161600/1615248000

Should easily fall in-range with the other sales

History 10: https://backpack.tf/item/9141618146

Sold to a bot:

https://backpack.tf/profiles/76561198027629227#!/compare/1612828800/1612915200

https://backpack.tf/profiles/76561199098725833#!/compare/1612828800/1612915200

Untraceable:

https://backpack.tf/profiles/76561199098725833#!/compare/1613001600/1613088000

https://backpack.tf/profiles/76561198224899376#!/compare/1613088000/1613347200

Untraceable:

https://backpack.tf/profiles/76561198224899376#!/compare/1613088000/1613347200

https://backpack.tf/profiles/76561198207924905#!/compare/1613174400/1613692800

Other Marketplace.tf sale: https://marketplace.tf/items/tf2/31115;5;u155

April 14: $89.99/2.08=43.26 ~43 keys

Unsolds:

40 keys for 2 months https://backpack.tf/item/9226029556

Marketplace.tf at ~45 keys https://marketplace.tf/items/tf2/31115;5;u155

Sales at 28, 30, 34, 35, 38, 43

Given the unsold at 2 months for 40 keys, 43 looks like an outlier. Buyers up to ~29.03 indicate 28 will be low too https://gladiator.tf/listings/6084625210cf2da274256927

Going with 30-38 here with an outlier on each end