33 in existence, only 3 sellers. Thanks to Foamy for helping me with the subject of Unique Spec KS weapons!

Sale 1:

https://backpack.tf/profiles/76561198096210931?time=1445324400&compare=1445410800

Sold for G. Fetti Janissary Ketche (ignore the miscellaneous garbage, it was a 1/1)

Ketche Mini:

http://imgur.com/TJVsQYF , http://imgur.com/ETFzXQv

Sold for 8 pure

8*.9 = 7.2 (Ketche was offered) I'm gonna go ahead and call this one an outlier.

Sale 3:

https://backpack.tf/profiles/76561198096210931?time=1445497200&compare=1445410800

Sold for an Orbiting Planets Halogen Headlamp.

x = 11.5 (DeGroot was offered), rounding up to 12. Using as high end.

Sale 2:

https://backpack.tf/profiles/76561198176297517?time=1449388800&compare=1449302400

Sold for a Pro KS Aussie Axtinguisher and a Spec KS Soda Popper (using 15 ref for the Popper, rounding up to 1 key).

Lowest price for Axtinguisher at the time of this suggestion: http://imgur.com/iYF3r1S

x = 8.84 + 1

x = 9.84 , rounding up to 10. Using as low end.

Sale 3:

https://backpack.tf/profiles/76561198164381061?time=1448697600&compare=1449302400

Sold for a KaW YoBB. Can't find a suitable mini, so not using.

Can't seem to track the other sales in this one's history.

Sellers:

http://www.tf2outpost.com/trade/27422736

Poorly bumped, hasn't received any offers.

http://www.tf2outpost.com/trade/27457991

Has had it in his backpack for over 3 months, as shown here: https://backpack.tf/profiles/76561198025208249?time=1441436400 , so not valid.

Can't find any other sales. Feel free to let me know if I did anything wrong in the comments!

http://puu.sh/lM8vG/d4cca28804.png

Sold for 15 ref, 2 keys, a partless Strange Pro KS YeR and a Killstreak Festive Ambassador.

0.93 + 2.39 + 0.58 + 2 = 5.89. Gonna say this is an outlier.

http://puu.sh/lM8Jq/b8bfd17d27.png

Sold for Massed Flies Bonnet and a pair of Earbuds.

Massed Flies Bonnet Mini;

http://backpack.tf/profiles/76561198113571653?time=1446274800&compare=1446361200

I believe it sold for 8 keys 8 ref. Can't find another sale.

x = 2.85 + 8.5 (keys were 16.11 back then)

x = 11.35. Supports my current price range.