Sale #1:

Sold for $64.99 on the market (seller recieved $56.53) ~23-26 keys at $2.49 per key

http://backpack.tf/item/1772198260

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

Sale #2:

Sold for 23 keys + Pro KS Unique Scattergun (~4 keys on SCM)

http://backpack.tf/profiles/76561198085546246?time=1442041200 (September 12th)

http://backpack.tf/profiles/76561198085546246?time=1442818800 (September 21st)

23 + 4 = 27 keys

Sale #3:

http://www.tf2outpost.com/trade/26962017 Sold for 27 keys

http://backpack.tf/profiles/76561198130148331?time=1441522800 (September 6th)

http://backpack.tf/profiles/76561198130148331?time=1441609200 (September 7th)

Sale #4:

http://www.tf2outpost.com/trade/26875767

Sold with 11 keys for GE Batter's (39)

(39 * 0.9) - 11 = 24 keys

Sale #5:

http://www.tf2outpost.com/trade/26831059

Sold for PFetti Pipe (outdated)

http://backpack.tf/profiles/76561198079404789?time=1440054000 (August 20th)

http://backpack.tf/profiles/76561198079404789?time=1440226800 (August 22nd)

Sale #6:

http://www.tf2outpost.com/trade/27168876 Sold with other stuff for a gold pan

~

This lines up perfectly with Steaming's value. :D