Thanks to Burny for letting me resuggest this!

Added more recent sales.

https://marketplace.tf/items/434;5;u59

19,99/1,94=10 keys

22,99/1,99=11.5 keys countered by 2 month unsold for 11

24,99/1,94=13 keys countered by 2 month unsold for 11

15.86/1.89=8.4 keys

https://backpack.tf/profiles/76561198171294857#!/compare/1529193600/1532649600

https://backpack.tf/profiles/76561198273803651#!/compare/1528502400/1529280000

untrace

https://backpack.tf/profiles/76561198197481041#!/compare/1533168000/1533254400

bulk

https://backpack.tf/profiles/76561198002757046#!/compare/1532476800/1532563200

https://backpack.tf/profiles/76561198373868152#!/compare/1532476800/1532563200

untrace, was prolly qs anyway since its to Rubi

https://backpack.tf/profiles/76561198125791160#!/compare/1528934400/1529020800

https://backpack.tf/profiles/76561198103764157#!/compare/1524787200/1529020800

with 12 keys for Magnetic Hat Protector Universal Translator(18)

6 lol

https://backpack.tf/profiles/76561198275179429#!/compare/1526601600/1526688000

https://backpack.tf/profiles/76561198412089276#!/compare/1526515200/1526688000

10 keys that dont match rip

https://backpack.tf/profiles/76561198412089276#!/compare/1526515200/1526688000

https://backpack.tf/profiles/76561198275179429#!/compare/1526601600/1526688000

Ancient Codex A Head Full of Hot Air(8.75)

https://backpack.tf/profiles/76561198083892088#!/compare/1527292800/1527379200

https://backpack.tf/profiles/76561198275179429#!/compare/1527206400/1527292800

Bubbling Tavish DeGroot Experience

should be used there

https://backpack.tf/profiles/76561198216968391#!/compare/1527379200/1527465600

https://backpack.tf/profiles/76561198083892088#!/compare/1527379200/1527465600

untrace

https://backpack.tf/profiles/76561198216968391#!/compare/1527465600/1530316800

https://backpack.tf/profiles/76561198277317599#!/compare/1527292800/1527638400

nothing matches

https://backpack.tf/profiles/76561198277317599#!/compare/1527638400/1527724800

https://backpack.tf/profiles/76561198154186837#!/compare/1527638400/1527724800

with 2 keys for Orbiting Fire Bonk Helm

should be used there

https://backpack.tf/profiles/76561198125350415#!/compare/1529107200/1529193600

bulk

https://backpack.tf/profiles/76561198125350415#!/compare/1531353600/1531440000

https://backpack.tf/profiles/76561198312265776#!/compare/1531267200/1531353600

untrace

https://backpack.tf/profiles/76561198002757046#!/compare/1534377600/1534464000

https://backpack.tf/profiles/76561198162873354#!/compare/1534377600/1534464000

10 keys, countered by below sale

https://backpack.tf/profiles/76561198162873354#!/compare/1534464000/1534896000

https://backpack.tf/profiles/76561198231040628#!/compare/1534377600/1534464000

8 keys, countered by above sale

https://backpack.tf/profiles/76561198231040628#!/compare/1534464000/1534550400

https://backpack.tf/profiles/76561198731436153#!/compare/1534550400/1534723200

TW Bonk Helm

should be used there

https://backpack.tf/profiles/76561198212896283#!/compare/1532649600/1532736000

untrace

https://backpack.tf/profiles/76561197984373540#!/compare/1532476800/1532649600

https://backpack.tf/profiles/76561198212896283#!/compare/1532563200/1532649600

untrace

https://backpack.tf/profiles/76561197984373540#!/compare/1532390400/1532476800

bulk

https://backpack.tf/suggestion/5b6dc56acf6c75494352b89e

Going off of previous suggestion mod comments, lets take 9 - 10 keys.