All of the proof belongs to Bob and Electrostatic, I'm merely correcting their range.

Counter-suggestion

Sold for GE Swatter + ~3 Keys:

http://backpack.tf/profiles/76561198051310874?time=1440449359

=66 Keys

Sold with Pro Aus Ax for Burning Little Buddy:

http://backpack.tf/profiles/76561198057160393?time=1437774567

=82 Keys, Outlier

http://www.tf2outpost.com/trade/26874289

~Sold for PE Salty Dog and 5 Keys

=61 Keys

Backpack before:

http://backpack.tf/profiles/76561198051310874?time=1442223092

Backpack after:

http://backpack.tf/profiles/76561198051310874?time=1442386800

Mini for PE Salty:

Pending sugg. 56 Keys, but with pure sale

=56 Keys

Sold with a DBD Baron Von Havenaplane and Str All-Father for a Scorching Fukaamigasa

http://backpack.tf/profiles/76561198076645019?time=1439622000

http://backpack.tf/profiles/76561198076645019?time=1439794800

=51 Keys, Outlier

Havenaplane:

http://www.tf2outpost.com/trade/27099095

~Sold for a Eerie Tam O' Shanter + 1 Bud + Spec Ks Collector's Chaidheamh Mor + 7 Keys

B/O Cap at 30

To show its not too high:

Sold for Nursey's Spec Aus Medigun:

http://backpack.tf/profiles/76561197969363424?time=1440298806

Regular spec aus medigun has sellers of ~30, so this sale is at least 30.

51 is low, 82 is high. 61-66 meet as a midpoint for all the sales, while still being the most common. It also doesn't help that those two sales were bulk sales.

61-66 Keys should be fine.

Additional Proof/Counter-Proof/Constructive Criticism/Feedback is always appreciated.