It's been 3 months and I see some changes. Proof in the comments. :3

*UNSOLD*

http://www.tf2outpost.com/trade/8274570 ( Unsold for 1 week at 3.33 ref. )

http://www.tf2outpost.com/trade/8417112 ( Unsold for 1 day at 3 ref, was offered 2.88 ref, but rejected it, "kinda funny imo" )

http://www.tf2outpost.com/trade/8070596 ( Unsold for 2 weeks at 3.33 ref. )

http://www.tf2outpost.com/trade/8405181 ( Unsold for 2 days at 3 ref. )

http://www.tf2outpost.com/trade/8447564 ( Unsold for 7 hours at 3.33 ref, not going to count it in the suggestion, but the price matter )

http://www.tf2outpost.com/trade/8439521 ( Unsold for 17 hours at 3 ref, again, not going to count )

http://www.tf2outpost.com/trade/8402634 ( Unsold for 2 days at 3 ref )

http://www.tf2outpost.com/trade/8370418 ( Unsold for 3 days at 3 ref )

"As you can see, selling it for 3.33 ref is getting hard. Selling it for 3 ref is kinda tricky as well, but no less, there are buyers at 3 ref." :)

*BUYING*

http://www.tf2outpost.com/trade/8419020 ( Buying for 3 ref, found a seller )

http://www.tf2outpost.com/trade/7973901 ( Bought 1 or 2 for 2.66 ref )

"Seeing someone is buying it for 3 ref does show the price at 3 ref is valid, but he was also the only buyer at 3 ref. I found another buyer that bought 1 or 2 for 2.66 ref each, which 'could' be considered a 'quick-buyer' but no less, he has bought 1 or 2 within a week, so I would consider it valid." :/

Conclusion: 3.33 ref isn't working any more. 3 ref is hanging in there, but again, it's tricky. I will set the lower value to 2.66 ref, because the guy managed to buy 1 or 2 PnS for 2.66 ref within a week.