I will try to price this. Here goes. :D

Classifieds:

http://backpack.tf/classifieds/search/id/52a278254cd7b80e118b4595

3 at 3 ref / Only one below 3, which is really young

Solds at 3 ref:

http://www.tf2outpost.com/trade/16279401

http://www.tf2outpost.com/trade/16346105

http://www.tf2outpost.com/trade/16273176

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http://www.tf2outpost.com/trade/16212747 - offer of 3 ref

Sellers at 3 ref:

http://www.tf2outpost.com/trade/16331432 - 2,88 ref, selling 2 (Close enough to 3 :) )

http://www.tf2outpost.com/trade/16259489 - Not bumped

http://www.tf2outpost.com/trade/16346287 - Selling 2

http://www.tf2outpost.com/trade/16359433 - Selling 3

http://www.tf2outpost.com/trade/16329394

http://www.tf2outpost.com/trade/16354096 - Untradeable xD (Tradeable in 5 days~)

Some unsolds at higher than 3 ref (To show that above 3 doesn't happen~) :

http://www.tf2outpost.com/trade/16350785 - 4 ref

http://www.tf2outpost.com/trade/16331191 - 4 ref

http://www.tf2outpost.com/trade/16314495 - 5 ref

http://www.tf2outpost.com/trade/16327117 - 5 ref

http://www.tf2outpost.com/trade/16274504 - 1 key

http://www.tf2outpost.com/trade/16223880 - 1 key

http://www.tf2outpost.com/trade/16340153 - 1 key

http://www.tf2outpost.com/trade/16327633 - 1 key

http://www.tf2outpost.com/trade/16213676 - 1 key

http://www.tf2outpost.com/trade/16238769 - 1 key

http://www.tf2outpost.com/trade/16331199 - 1,1 keys ..

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http://www.tf2outpost.com/trade/16365942 - 1 ref instasold

Almost none below 3 on market. And above doesn't seems to happen or happens rarely. :) 3 seems like a good price for now.