Well. If duped one has been sold for more than backpack price, we know that the hat needs a rise.

Sale 1

http://www.tf2outpost.com/trade/25440291 - Sold for a Morning Glory Tough Guy's Toque (4.9 buds) + Professional Killstreak Minigun (1.3 buds) + 2 buds + 2-key in sweet (6.3*0.9 + 2.3 = 8 buds)

Mini for the Morning Glory Tough Guy's Toque

http://www.tf2outpost.com/trade/25525303 - Offered on a Circling Heart Reggaelator (4.9 buds). No overpay.

Sale 2

http://www.tf2outpost.com/trade/25402742 - Offered on my Green Black Hole Wraith Wrap (BO 7 buds) (Outlier)

Yep, both sales won't be used as the hat is duped. The clean one got offered a lot of more in pure.

http://www.tf2outpost.com/trade/20841331 - Got an offer of Max Head + 5 buds + sweet (Max = 39 keys = 3.3 buds atm) (8.3 buds)

It's safe to say that 8.3 is fine.

Feel free to counter / support my proofs.