Sale #1:

http://www.tf2outpost.com/trade/28470557 Wanted 15 keys (relisted numerous times)

http://backpack.tf/profiles/76561198049398059#!/compare/1473120000/1473206400

Difficult to trace what the sale was (the history on the Mullet isn't matching). This sale would likely cap at 15 keys regardless.

Sale #2:

Sold for a Purple Confetti Handle (14 keys in mini) + ~1 key in items

http://backpack.tf/profiles/76561198077304230#!/compare/1473120000/1473206400

http://backpack.tf/profiles/76561198192318630#!/compare/1473120000/1473206400

14 + 1 = 15 keys

Purple Confetti Handle:

Purple Confetti Handle + ~1 key in items sold for Pro KS Australium FaN (~15 keys)

http://backpack.tf/profiles/76561198077304230#!/compare/1473206400/1473292800

15 - 1 = 14 keys

One Purple Confetti Handle has been unsold for 4 months:

http://i.imgur.com/kP3AaST.png

Sale #3:

Sold for Nuts Phantom (18 keys in mini)

http://www.tf2outpost.com/trade/28306933

https://backpack.tf/profiles/76561198192602363#!/compare/1468195200/1468281600

https://backpack.tf/profiles/76561198271894393#!/compare/1468195200/1468281600

18 keys

Nuts Phantom:

Nuts Phantom is just barely outdated

http://i.imgur.com/ff7FCLP.png Unsold at 18 keys for 2 months, buyers at 16 keys. Value should be around 18 keys

Sellers:

http://i.imgur.com/bdeUi2H.png 2 months at 18 keys

Conclusion:

All sales are within suggested range.