Caffeine.

https://backpack.tf/item/921601519

Sale 1) Sold for a Kill-a-Watt Chieftain's (21.5 Keys) + Cloud 9 Juju (15 Keys) + Smoking Cowl (13.5 Keys) + Memory Leak Plumber's (9.5 Keys) + 5 Keys

https://backpack.tf/profiles/76561197998934095#!/compare/1546041600/1546214400

21.5 + 15 + 13.5 + 9.5 + 5 = 64.5, which rounds to 65 Keys

Challenge Mini

https://backpack.tf/suggestion/5c4824cb44325a16086e83d4 - 21.5 Keys

Plumber's Mini

https://backpack.tf/suggestion/5c438f6bcf6c752fa61179c8 - 9.5 Keys

Sale 2) Sold + 11 Keys + Bubbling Backbiter's Billycock for a Chiroptera Venenata Bootleg Base Metal Billycock

https://backpack.tf/profiles/76561198085880346#!/compare/1547510400/1547942400

Using this sale to update the Billycock.

Sale 3) Sold fairly quickly for 43 Keys

https://imgur.com/a/WUejqGh

This sale took ~2 - 3 days and was under the Seller's buyout price. Counting this as low.