It's pretty evident that no one wants to sell it in the current range, since it is considered the god tier hat for medic with a pretty fitting effect. This hat is prized among flies collectors and coincidentally that's where most of them are right now if they aren't with the unboxer still. Most of these collectors will deny offers above what my suggested range is, but there are some for sale. The price is 9 months old with no real proof, so it seems like it needs some touching up. There's 3 of them on outpost, so the proof is a bit lacking here but I will try to go into each one into detail.

I've been searching item histories of this hat and none of the sales are really recorded unfortunately. If you get any more info, please feel free to comment below.

Trade 1:

http://www.tf2outpost.com/trade/9883337

-Offered 50 keys pure, didn't accept and the seller says this is "not even close". This is about 2.4 buds, which is still in the current range but it goes to show that the middle of the current range isn't represented very accurately.

Trade 2:

http://www.tf2outpost.com/trade/8925143

-Offered an Orbiting Fire Voodoo Juju (valued at 2.5-3.0 buds) that he did not accept. Higher end of that hat is out of current range, and even taking unusual overpay into account this shows that the middle of the range is not being represented well.

-1 bud + 1 bills + untradeable vintage Crusader's Crossbow. Take this one with a grain of salt, highest I see a Crossbow going for is here (http://www.tf2outpost.com/trade/10198750), which is nowhere close to the buyout.

-Offered Steaming Anger (2.3-2.6), which is in range.

Trade 3:

http://www.tf2outpost.com/trade/10177084

-Offered 2 buds + BaF Bill's, about 2.4 pure again. Did not accept, showing the middle of the range isn't represented very well.

Misc:

http://www.tf2pricecheck.net/Thread-PC-Massed-Flies-Vintage-Tyrolean?page=3

-General consensus here seems to be at 3 buds solid, but some think 2.5-3 is better.