Proof:

Last Suggestion (Credits to FalconFlyer42):

http://www.tf2outpost.com/trade/6618590 (2 Sold/Added for 4.33, 1 for 4.88)

http://www.tf2outpost.com/trade/16781150 (Receives an offer of 4 refined, and turns down a painted anger worth 8.36 refined.)

http://www.tf2outpost.com/trade/16895605 (Turns down many offers of 3.33 and one offer of 3.55, and sells one for a key.)

http://www.tf2outpost.com/trade/17497844 (Sold at 5 ref)

http://www.tf2outpost.com/trade/17468363 (2 sold at 4 refined, note that for me I ended up paying 4 refined.)

My Proof:

Sales at 4 ref:

http://imgur.com/91tRUnC - 2 sales

http://www.tf2outpost.com/trade/17696308 - Sold for 3.88 without a bump, 3 views

http://www.tf2outpost.com/trade/17666638 - Sold for 3.88 without a bump

http://www.tf2outpost.com/trade/17659534 - Less than a day

http://www.tf2outpost.com/trade/17660495 - Less than a day

http://www.tf2outpost.com/trade/17675058 - Less than a day

http://www.tf2outpost.com/trade/17683421 - Less than 12 hours

http://www.tf2outpost.com/trade/17691133 - Less than 5 hours

http://www.tf2outpost.com/trade/17690494 - Less than 2 hours

http://www.tf2outpost.com/trade/17687380 - Without a bump

http://www.tf2outpost.com/trade/17670195 - Without a bump

http://www.tf2outpost.com/trade/17662393 - Without a bump

http://www.tf2outpost.com/trade/17666628 - Without a bump

http://www.tf2outpost.com/trade/17658074 - Sold for 4.33 in less than a day

http://www.tf2outpost.com/trade/17681829 - Sold for 4.33 in less than 11 hours

http://www.tf2outpost.com/trade/17658123 - Sold for 5 in less than a day

I can find more quicksells below 4 but 2 sales at 3.88 (which is 1 scrap below 4) sold without a bump, 1 with just 3 views...

The amount of 4 sales from the past 2 days and the time it took also show that 4 is almost a quicksell

Adding 2 pretty fast sales at 4.33 and 1 at 5, I think that a range is really unnecessary and 4 flat is the most accurate and most commonly traded price