Proof below. 3 month-old price.

Sales:

http://www.tf2outpost.com/trade/15166020

-b/o of 5.5 buds

-sold for 4 buds+smoking country=~4.9 buds

http://www.tf2outpost.com/trade/15163785

-b/o of 6 buds

-billy+aces (unpriced) and steaming brigade sold for stormy gibus

http://www.tf2outpost.com/user/76561198040780597

-this user seems to have sold/bought the same hat for stormy attendant (not in history)+o.f. phantom: http://www.tf2outpost.com/trade/15162734

-seller's bp:

http://backpack.tf/id/76561198040780597?time=1382166000

http://backpack.tf/id/76561198040780597?time=1382252400 (phantom sold for fedora)

-keys here bought the attendant: http://www.tf2outpost.com/trade/15158404

-3.7 buds, outlier

http://www.tf2outpost.com/trade/14920219

-sold for flies kabuto+1 bud+sf medi gun=~4.7 buds

http://www.tf2outpost.com/trade/14792661

-wanted 5 buds

-sold for miami fez=~3.6 buds, outlier

http://www.tf2outpost.com/trade/16126750

-quicksold for 2 buds :(

http://www.tf2outpost.com/trade/14979608

-b/o of 6 buds

-sold for 6 buds, clear outlier looking at b/os

Current trades:

http://www.tf2outpost.com/trade/15531674

-notable offers:

vivid phantom=3.8

burning panama (we'll see)=4

c9 fez (outdated)=3.9

http://www.tf2outpost.com/trade/16183409

-b/o of 7 buds

-notable offers:

cloudy billy (outdated)=3.9

cauldron phantom=4.9

http://www.tf2outpost.com/trade/13804094

-wants 7 buds, few months old

-recent notable offers:

pe bolted birdcage+31 keys=3.9

4 buds+smoking big country (bought one in a sale above)

http://www.tf2outpost.com/trade/16111809

-b/o of 5 buds, 1 week (has had it much longer than that)

-notable offers:

burning panama=4

demonflame cosa (almost finished suggestion)=~4.7

cloudy pith=4

As you can see, this is a pretty difficult hat to update with few sales and few good offers. Offers aren't as good as the sales but sales>offers in in terms of importance. 3.6 and 3.7 are outliers looking at the 4.7 and 4.9 sales as well as the 6 buds (outlier). Would be impossible to get this with a 3.7 bud offer. Anyway there are 2 offers between my range. 4.7-4.9 seems to be the best price for this for now. Unusual overpay and original prices used.