This needs an update

Sellers @ 1.5 keys:

http://www.tf2outpost.com/trade/14358372 - Sold within 4 hours

http://bazaar.tf/trade/421099 - Sold within 4 hours

http://www.tf2outpost.com/trade/14354841 - Sold

http://backpack.tf/classifieds/search/id/520122684bd7b87d05000010 - Both parts sold out

http://bazaar.tf/trade/408277 – Sold

http://www.tf2outpost.com/trade/14324290 – Buying for 1.5 keys

http://bazaar.tf/trade/413592 – Selling for 9 ref

Sellers @2 keys:

http://www.tf2outpost.com/trade/14304288 – Sold for White paint (2-2.4 keys)

http://bazaar.tf/trade/418906 - My own trade. Sold

http://tf2tp.com/trade.php?trade=9774717 - Sold

http://www.tf2outpost.com/trade/14025730 - Got atleast 4 adds for critical kills parts. Rest are ambiguous

http://www.tf2outpost.com/trade/10175254 - Crit Kills sold out @2 key price

http://www.tf2outpost.com/trade/14030050 - Selling @2 keys with some success

Other sellers

http://www.tf2outpost.com/trade/13888656 - Selling for 3 keys, Offered 2 keys week back

http://www.tf2outpost.com/trade/11984187 - Selling for 3 keys. Not much success

http://www.tf2outpost.com/trade/11255905 – Inactive for months. Been offered 1.5 keys multiple times, no response from OP

http://www.tf2outpost.com/trade/9078160 - Looking for offers. Turned down 1.5 key offers

http://bazaar.tf/trade/248347 – Looking for offers. Offered 1.5 keys on multiple counts

There are only like a handful of people selling this. Search page yields only one page of result with about 10 individuals selling it. Critical Kills gets sold real quickly if you put it up for 1.5 keys and are actively trading. Even sellers selling at 2 keys are having a decent success rate given short supply