Sale 1

Sold with 5 keys for D@D Voodoo

http://backpack.tf/profiles/76561198115499745/#!/compare/1459036800/1459123200

X + 5 = 70

X = 65

Sale 2

Sold for Circling TF Fed + 12 keys

http://backpack.tf/profiles/76561198075816743/#!/compare/1458950400/1459123200

Fed Mini

Sold for 60 keys pure

http://backpack.tf/profiles/76561198135234107/#!/compare/1456992000/1457337600

Sold for Stormy 13th Sober

http://backpack.tf/profiles/76561198111350827/#!/compare/1455004800/1455177600

Sober Micro

Sold for 50 keys

http://backpack.tf/profiles/76561198214057529/#!/compare/1455696000/1455782400

B/O cap at 65: http://www.tf2outpost.com/trade/27962399

X = 65

Sale 3

Sold for Haunted Ghost Hermes + 28 keys

http://backpack.tf/profiles/76561198055789548/#!/compare/1457596800/1457683200

Hermes Mini

Sold for 26 keys

http://backpack.tf/profiles/76561198083856665/#!/compare/1457424000/1457596800

X = 54

Sale 4

Sold for 60 keys pure

http://backpack.tf/profiles/76561198055789548/#!/compare/1457683200/1457769600

Extra info: http://www.tf2outpost.com/trade/27944752

X = 60

Sale 5

Sold for 62 keys + 4 keys of sweets

http://backpack.tf/profiles/76561198065347016/#!/compare/1454745600/1455004800

X = 66

Conclusion: 54 seems like an outlier (far from B/O of 60 http://www.tf2outpost.com/trade/27943231). Price range from 60 to 66.