I made an actual suggestion for the planets HKC one time.

I wish it were as easy as this one is.

Sold for 30 Keys and ~6 Keys in Sweets(36 Keys total)

http://backpack.tf/profiles/76561198043936328#!/compare/1482796800/1482883200

Sold for a Steaming Vive La France(33.5 Keys, round to 34) and 8 Keys(42 Keys total)

http://backpack.tf/profiles/76561197982127154#!/compare/1485388800/1485475200

Sold for a Steaming Cotton Head(29 Keys) and 11 Keys(40 Keys total)

http://backpack.tf/profiles/76561198188110526#!/compare/1485820800/1485907200

36-42.

Credits to Mindacos for the suggestion. He found the proof, I'm just posting it.