This is a very conservative suggestion. There are many sellers at 1.66-2 ref, but there are also a lot sold/offered at 2.66-3 ref. I didn't feel like making this 1.66-3 ref because that would be way too big. This can be refined later.

Classifieds have a few spread out from 1.66-3 ref: http://backpack.tf/classifieds/search/30020/6/0

Buyers

http://www.tf2outpost.com/trade/11026307 1.66 ref

http://www.tf2outpost.com/trade/11020331 1.66 ref

Offers

http://www.tf2outpost.com/trade/10949698 1.66 ref

http://www.tf2outpost.com/trade/10925933 2 craft hats (~2.66 ref)

http://www.tf2outpost.com/trade/10879777 2.66 ref

http://www.tf2outpost.com/trade/10966177 3 ref

Sold

http://www.tf2outpost.com/trade/10934549 1.33 ref

http://www.tf2outpost.com/trade/10996968 1.66 ref

http://www.tf2outpost.com/trade/11005621 1.66 ref

http://www.tf2outpost.com/trade/10982051 2 ref

http://www.tf2outpost.com/trade/11033392 2 ref

http://www.tf2outpost.com/trade/10927933 3 ref, 5 hrs ago

http://www.tf2outpost.com/trade/10976573 3 ref, 7 hrs ago

http://www.tf2outpost.com/trade/10997882 3 ref, 9 hrs ago

http://www.tf2outpost.com/trade/10951049 3 ref, 2 days ago

http://www.tf2outpost.com/trade/10919581 4 ref

Sellers

http://www.tf2outpost.com/trade/10995833 1 ref

http://www.tf2outpost.com/trade/11020820 1.66 ref

http://www.tf2outpost.com/trade/11037060 1.66 ref

http://www.tf2outpost.com/trade/10962038 1.66 ref

http://www.tf2outpost.com/trade/10968135 2 ref (Spreadsheet)

http://www.tf2outpost.com/trade/10968240 2 ref

[url]http://www.tf2outpost.com/trade/10981722[/url] 2 ref Sold

http://www.tf2outpost.com/trade/10989407 2 ref

http://www.tf2outpost.com/trade/11030884 2 ref

http://www.tf2outpost.com/trade/11033792 2 ref

http://www.tf2outpost.com/trade/11035748 2 ref

http://www.tf2outpost.com/trade/11039025 2 ref

http://www.tf2outpost.com/trade/10981351 2.33 ref

http://www.tf2outpost.com/trade/11034095 Scrap Pack + 0.66 ref (2.33-2.66 ref)

http://www.tf2outpost.com/trade/10978519 2.66 ref

http://www.tf2outpost.com/trade/10982620 2.66 ref, Sold 1/2

http://www.tf2outpost.com/trade/11042690 2.66 ref

http://www.tf2outpost.com/trade/11009223 3 ref

http://www.tf2outpost.com/trade/11008715 3 ref