There's some crazy stuff in this suggestion.

Sale 1:

Sold alongside a Strange Pro KS Degreaser, Strange Pro KS Shotgun and Collector's Pro KS Powerjack for ~37 mixed keys and a 3 key item.

http://www.tf2outpost.com/trade/27891725

http://i.imgur.com/iHsrQ3l.png

The Degreaser and Shotgun sold for 12 TF2 keys, and the Powerjack sold for 10: http://i.imgur.com/Ryjtu6W.png

Thus putting the Bubble Pipe at about 6/7 TF2 keys. Not using.

Sale 2:

Sold for a Circling Peace Sign Fortunate Son.

http://backpack.tf/profiles/76561198067161406/#!/compare/1457938800/1458111600

http://www.tf2outpost.com/trade/27937196

Buyout was 80 keys, capping at 80.

1 of 1 with two recent sales, pretty clear which is the outlier here.

Feedback is welcome and appreciated.