Sale 1:

Item: https://backpack.tf/item/551764099

Seller: https://next.backpack.tf/profiles/76561198198512711/compare?from=1730764800&to=1731110400

Buyer: https://next.backpack.tf/profiles/76561198379906251/compare?from=1731024000&to=1731110400

Sold for 470 Pure.

Sale 2:

Item: https://backpack.tf/item/551764099

Seller: https://next.backpack.tf/profiles/76561199579303448/compare?from=1728259200&to=1728345600

Buyer: https://next.backpack.tf/profiles/76561198113190503/compare?from=1728259200&to=1728432000

Sold w/ Death at Dusk Modest Pile of Scrap for 520 Pure (Modest Pile @ 135) ~385 Pure

Sale 3:

Item: https://backpack.tf/item/551764099

Seller: https://next.backpack.tf/profiles/76561198113190503/compare?from=1728518400&to=1728604800

Buyer: https://next.backpack.tf/profiles/76561198198512711/compare?from=1728518400&to=1728604800

Sold for Morning Glory Dread Hiding Hood (210 Keys) + Morning Glory Ol' Snaggletooth (92 Keys) + PE Crit Cloak (Old Price, Mini Below) ~402 Mixed

Sale 4:

Item: https://backpack.tf/item/551764099

Seller: https://next.backpack.tf/profiles/76561199127773728/compare?from=1733011200&to=1733184000

Buyer: https://backpack.tf/profiles/76561198045041209#!/compare/1733097600/1733184000

350 pure + Pro KS Pan (~70) + Black Uncraftable Flip-Flops + Uncraftable Lucky No. 42 = 442 Mixed

Sale 5:

Item: https://backpack.tf/item/551764099

Seller: https://next.backpack.tf/profiles/76561198103213778/compare?from=1730332800&to=1730592000

Buyer: https://backpack.tf/profiles/76561199127773728#!/compare/1730505600/1730592000

Unclear, but maybe 237 pure? Outlier, perhaps a quicksale.

Seems like 385 - 470 is a solid (albeit large) range.

Mini for Crit Cloak:

Buyers @ 84 keys: https://next.backpack.tf/classifieds?itemName=Crit%20Cloak&quality=5&particle=10

Listed on Marketplace.tf for $199.99

https://marketplace.tf/items/tf2/30899;5;u10

Sale 1:

Listed on Mannco for $169.98 (with a recent sale on 10/31 for the same price) 169.98 / $1.71 = 99.4 keys

https://mannco.store/item/440-purple-energy-unusual-crit-cloak

Sale 2:

Item: https://backpack.tf/item/15166972348

Seller: https://next.backpack.tf/profiles/76561198113190503/compare?from=1731888000&to=1732665600

Buyer: https://next.backpack.tf/profiles/76561198050223063/compare?from=1732060800&to=1732233600

Sold for PE Climbing Commander (mini-mini below) + Max's + Glamorous Dazzle Profane Puppeteer (no listings other than mannco @ 24.97 and buyers on classified at 2 keys. One sale @ $8.06 back in May) = ~122 Mixed

Averaging to 111 keys.

Mini-mini for PE Climbing Commander:

Sale 1:

Recent sale @ Marketplace for $159.99 / $1.71 = 93.5 keys

https://marketplace.tf/items/tf2/31025;5;u10

Sale 2:

Item: https://next.backpack.tf/item/15156496691

Buyer: https://next.backpack.tf/profiles/76561198112556959/compare?from=1733011200&to=1733184000

Seller: https://next.backpack.tf/profiles/76561198113190503/compare?from=1733011200&to=1733184000

(I can't seem to get the item to appear in the buyer's inventory, but the keys all come from his backpack. Not sure why this is the case.)

Sold for 70 keys pure.

~81.5 keys.

This is my first suggestion in nearly a decade - please let me know if everything checks out.

I used $1.71 as the key price from Russel's large suggestion. His key mini should be up to date.