Sale 1: (outlier, quicksell)

Sold for 20 keys pure

20 keys

http://www.tf2outpost.com/trade/25055307

Sale 2:

Sold with a Steaming Honcho's Headgear for 34 keys plus ~3 keys of sweets plus 40 ref (keys were 16.66-17 then)

36.4 + (3*0.9) - 15.5 = 23.6 rounding to 24 keys

Before: http://backpack.tf/profiles/76561198101091782?time=1425801600

After: http://backpack.tf/profiles/76561198101091782?time=1425884400

Sale 3:

Sold with 1 key and ~2 keys of sweets for an Australium Scattergun.

(35*0.9) - 2 - 1 = 28.5 rounding to 29 keys

http://www.tf2outpost.com/trade/25574575

Before: http://backpack.tf/profiles/76561198154039852?time=1428390000

After: http://backpack.tf/profiles/76561198154039852?time=1428476400

Sale 4:

Sold for a Kill-a-Watt Caribbean Conqueror + a Duped Circling Peace Sign Larrikin Robin + a Bill’s

(8 + 3 + 17.5)*0.9 = 28.5 rounding to 29 keys

http://www.tf2outpost.com/trade/25714390 He forgot to close it

Before: http://backpack.tf/profiles/76561198154039852?time=1428994800

After: http://backpack.tf/profiles/76561198154039852

Notes:

Mini for the Duped Circling Peace Sign Larrikin Robin:

Sold for a strange frying pan + ~1 key of sweets

(9*0.9) = 8.1 rounding to 8 keys.

Before: http://backpack.tf/profiles/76561198055803408?time=1426921200

After: http://backpack.tf/profiles/76561198055803408?time=1427007600

Conclusion:

Sales at 24, 29, 29 and quick sale at 20. Taking the final range as 24 to 29 keys.