5 month old price!

Sale 1:

Sold for 15 keys

http://www.tf2outpost.com/trade/25723206

http://backpack.tf/profiles/76561198043568564?time=1429167600 (16th April)

http://backpack.tf/profiles/76561198043568564?time=1429254000 (17th April)

Sale 2: (outlier)

Sold with Professional Australium Flame Thrower* (21) + Sweets (~5) for Terror-Watt Modest (40*0.9)

X + 21 + 5 = 36

X = 10 keys

http://www.tf2outpost.com/trade/25647818

http://backpack.tf/profiles/76561198043568564?time=1428735600 (11th April)

http://backpack.tf/profiles/76561198043568564?time=1428822000 (12th April)

Sale 3:

Sold for Blizzardy Storm Pyro Beanie (13.5*0.9) + 14 keys = 12.15 + 14 = 26.15 (B/O was 22 keys)

http://www.tf2outpost.com/trade/26005724

http://backpack.tf/profiles/76561198031371895?time=1432710000 (27th May)

http://backpack.tf/profiles/76561198031371895?time=1432799851 (28th May)

Sale 4:

Sold for Australium Grenade Launcher (~17) + 2 keys = 17 + 2 = 19 keys

http://www.tf2outpost.com/trade/25912739

http://backpack.tf/profiles/76561198021291029?time=1431241200 (10th May)

http://backpack.tf/profiles/76561198021291029?time=1431500400 (13th May)

Sale 5: (invalid, too complex)

Involved in a bulk deal for a Duped Scorching Pyromancer's Mask

http://www.tf2outpost.com/trade/25863375

http://backpack.tf/profiles/76561198083717908?time=1431414000 (12th May)

http://backpack.tf/profiles/76561198083717908?time=1431500400 (13th May)

Mini-suggestion for Professional Australium Flame Thrower*: (after tax)

$55.96 | $55.97 | $53.04 | $50.00 | $47.83 | $53.00

Average value of $52.63 = ~21-22 keys

Conclusion:

Valid sales at 15, 19 and 22 keys. Taking a final price of 15-22 keys.

Feel free to support/counter my suggestion!