It's amazing to think although aaron last priced this, he could accept this suggestion...

Sale 1:

http://www.tf2outpost.com/trade/24928923 (Buyer's BP) http://backpack.tf/profiles/76561198158895899?time=1422950400 to http://backpack.tf/profiles/76561198158895899?time=1423036800 Sold in less than a day for 9 keys pure

Final sale vale: 9 keys (Outlier, because of how fast it sold and for how little compared to the current value)

Sale 2:

(No Outpost trade available) http://backpack.tf/profiles/76561197996391673?time=1422259200 to http://backpack.tf/profiles/76561197996391673?time=1422345600 Sold for a N&B Whoopie, worth 13.5 keys, 12 keys after overpay.

Final sale value: 12 keys

Sale 3:

(No Outpost trade available) http://backpack.tf/profiles/76561198083668125?time=1421654400 to http://backpack.tf/profiles/76561198083668125?time=1421913600 Sold with a N&B Stove Pipe, 11.5 keys/0.9 buds, for a DP Conqueror, 1.7 buds/22 keys

Final sale value: 9 keys (After overpay. Also seems to have sold in only a few days, and as it didn't have an Outpost trade, seems like an outlier)

As the first and third sales quicksold, the fact that the third sale doesn't seem that accurate because of the multiple unusuals being involved, and that almost anyone would buy most unusuals at 9 pure, 12 keys seems good. I couldn't trace any other sales in the last two months.