Basically full credits to K1ng. I was totally blind and forgot to check 1 history which had most of the recent sales.

Sale 1:

https://backpack.tf/profiles/76561198192602363#!/compare/1500595200/1500681600

Sold for 28 keys pure

Sale 2:

https://backpack.tf/profiles/76561198301623717#!/compare/1498348800/1498435200

Not sure.

Sale 3

Around ~25 in sweets

https://backpack.tf/profiles/76561198087402437#!/compare/1496188800/1496361600

https://backpack.tf/profiles/76561198378650078#!/compare/1496275200/1496361600

Sale 4

Heart Dead Cone (outdated at 24) + ~1 key

https://backpack.tf/profiles/76561198101327173#!/compare/1497312000/1497398400

https://backpack.tf/profiles/76561198378650078#!/compare/1497225600/1497398400

Sale 5

Mega Strike Buy A life (26) + ~2 keys in sweets

https://backpack.tf/profiles/76561198101327173#!/compare/1497484800/1497571200

Sale 6

Better to use this on the KE:

https://backpack.tf/profiles/76561198190084707#!/compare/1498003200/1498089600

Sale 7

21 keys in ~2 days

https://backpack.tf/profiles/76561198195731583#!/compare/1498176000/1498262400

https://backpack.tf/profiles/76561198301623717#!/compare/1498176000/1498262400

Sale 8

Strange Heart Elf Esteem

https://backpack.tf/profiles/76561198301623717#!/compare/1498348800/1498521600

https://backpack.tf/profiles/76561198039731024#!/compare/1498435200/1498521600

https://backpack.tf/suggestion/595bc9efcf6c75384c5e839f ----- Was used for the Elf.

Going with 25 - 28

Previous suggestion

https://backpack.tf/suggestion/5975c271cf6c753ccc12fc0b