1 key:

http://www.tf2outpost.com/trade/17124878

http://www.tf2outpost.com/trade/16805811

http://www.tf2outpost.com/trade/16693727

http://www.tf2outpost.com/trade/17242728 (claims to have had 5 in stock, now has 3, not certain)

6.33:

http://www.tf2outpost.com/trade/17237354

5 ref:

http://www.tf2outpost.com/trade/17237433

http://www.tf2outpost.com/trade/17222297

4.66:

http://www.tf2outpost.com/trade/17215894 ==> http://puu.sh/6lcxO.png

4.44:

http://www.tf2outpost.com/trade/17222622 ==> http://puu.sh/6lcrM.png

4.33 goes fast:

http://www.tf2outpost.com/trade/17252381 3 min

http://www.tf2outpost.com/trade/17252338 within a hour ==> http://puu.sh/6lbYh.png

http://www.tf2outpost.com/trade/17250539 without a bump

http://www.tf2outpost.com/trade/17242888 without a bump

http://www.tf2outpost.com/trade/17225965

4 ref goes fast as well

http://www.tf2outpost.com/trade/17247975 without a bump

http://www.tf2outpost.com/trade/17245210 2 hours

http://www.tf2outpost.com/trade/17242553 sold 12 in 5 hours ==> http://puu.sh/6lca0.png

http://www.tf2outpost.com/trade/17222749 ~a hour

http://www.tf2outpost.com/trade/17212474 ~a hour

so before you say there isn't that much proof for an item people stocked up alot on, it is because the sale is over and 99% of the people want to wait to sell for a key (price standard till sale)

alot of the people on outpost listed it for a key, which is a very hard and barely existing price to sell at.

Going with the very conservative 4.33 flat because making a proper range out of this is nearly impossible.