Sale 1:

Sold for a Cloud 9 Hetman's Headpiece and 2 keys of sweets

(16 + 2) = 18 keys

No outpost trade

http://backpack.tf/profiles/76561198064469074?time=1424851200 (February 25th)

http://backpack.tf/profiles/76561198064469074?time=1425024000 (February 27th)

Sale 2:

Sold with 10 keys for a Disco Beat Down Cotton Head

(30 - 10) = 20 keys

http://www.tf2outpost.com/trade/25835888

http://backpack.tf/profiles/76561198012570723?time=1431068400 (May 8th)

http://backpack.tf/profiles/76561198012570723?time=1431154800 (May 9th)

Sale 3: (outlier, quicksell)

Sold for X

Math

{outpost trade link}

Notes:

Mini for the Disco Beat Down Cotton Head:

Sold with 4 keys of sweets for a Vivid Plasma Grimm Hatte

(37.5*0.9) - 4 = 29.75 rounding to 30 keys

http://backpack.tf/profiles/76561198039013767?time=1429772400 (April 23rd)

http://backpack.tf/profiles/76561198039013767?time=1429858800 (April 24th)

Mini for the Cloud 9 Hetman's Headpiece:

Sold for a Bubbling Private Eye

(18*0.9) = 16.2 rounding to 16 keys

http://backpack.tf/profiles/76561198100888789?time=1427266800 (March 25th)

http://backpack.tf/profiles/76561198100888789?time=1427698800 (March 30th)

Conclusion:

Sales at 18 and 20,taking the final range at 18 to 20 keys.