Item: https://backpack.tf/item/4359793932

Sale #1

https://backpack.tf/profiles/76561198156255538#!/compare/1606435200/1606521600

Sold Circling Heart Dragonborn Helmet + 8 Keys and 29 ref (0.5 Key) for Haunted Ghosts Ye Olde Baker Boy (active suggestion at 32.5 Keys)

32.5 - 9 Keys = 23.5, rounding to 24 Keys [29 ref was 0.5 key. Keys were lower back then]

Sold for 24 Keys

Sale #2

https://backpack.tf/profiles/76561198138322150#!/compare/1604275200/1604361600

Bulk for Burning Flames Tough Stuff Muffs

Sale #3

https://backpack.tf/profiles/76561198081308147#!/compare/1606262400/1606521600

https://backpack.tf/profiles/76561198198091931#!/compare/1606176000/1606262400

Untraceable

Sale #4

https://backpack.tf/profiles/76561198060589954#!/compare/1606348800/1606435200

https://backpack.tf/profiles/76561198198091931#!/compare/1606262400/1606435200

Untraceable

Marketplace sales

Item: https://marketplace.tf/items/tf2/517;5;u19

28/1.87 = 14.97, rounding to 15 Keys [Oct 17]

44.85/1.84 = 24.38, rounding to 24 Keys [Oct 27]

Summary

Sales at

15 Keys

24 Keys

24 Keys

Conclusion

I'd go with 24 keys here, thanks.