Bzzt CLEAR

https://backpack.tf/item/1672322146

Sale 1) Sold for 14 Keys + ~2 Keys of Items

https://backpack.tf/profiles/76561198152089335#!/compare/1496620800/1497744000

Low Outlier.

Sale 2) Sold for a Miami Nights Scotsman's Stove Pipe (20.5 Keys)

https://backpack.tf/profiles/76561198260967101#!/compare/1501027200/1501113600

Rounds to 21 Keys

Stove Pipe Mini

https://backpack.tf/suggestion/599b3374cf6c752e94009047 - 20.5 Keys

Sale 3) Sold for a Duped Circling Peace Sign Professional's Panama (15.5 Keys) + 11.4 Keys

https://backpack.tf/profiles/76561198063640894#!/compare/1501545600/1501632000

15.5 + 11.4 = 26.9, which rounds to 27 Keys

https://backpack.tf/item/1654226589

Sale 4) Sold for 17 Keys + <0.5 Keys of Items

https://backpack.tf/profiles/76561198142023800#!/compare/1498262400/1498348800

Rounds to 17 Keys

Calling 17 low and 27 high (because of 3 lower sales) to take a conservative drop to 21 Keys.