Sale 1:

https://backpack.tf/profiles/76561198823739367#!/compare/1547683200/1547856000

https://backpack.tf/profiles/76561198163001029#!/compare/1547769600/1547856000

= 17 keys

Sale 2:

https://backpack.tf/profiles/76561198163001029#!/compare/1547942400/1548288000

(other side is unclear)

Untraceable/unclear

Sale 3:

https://backpack.tf/profiles/76561198080179568#!/compare/1550448000/1550534400

https://backpack.tf/profiles/76561198047988243#!/compare/1550448000/1550534400

= 20 keys

Sale 4:

https://backpack.tf/profiles/76561198823739367#!/compare/1544745600/1544832000

https://backpack.tf/profiles/76561198120566269#!/compare/1544054400/1544832000

= 15 keys + Strange Professional Killstreak Reserve Shooter (1.27 keys = 1 key + 12 refined metal) + 15 refined metal

= 16 keys + 27 refined metal

~ 17 keys

Marketplace.tf Sales

https://marketplace.tf/items/437;5;u64

= $30.99 / $1.75 (Jan 17th)

= 17.70...

~ 18 keys

= $25 / $1.73 (Dec 24th)

= 14.45...

~ 14 keys

Summary: 14, 17, 17, 18, 20

Conclusion: Excluding Dec 24th sale as it's below or equal to buy orders. Pricing at 17-20 keys.