Unpriced

Countersuggestion.

http://www.tf2outpost.com/trade/19705246

Offered on, and sold for, a Disco Beat Down Triboniophorus Tyrannus (4.4 buds w/ overpay)

http://www.tf2outpost.com/trade/20235892 -> http://www.tf2outpost.com/trade/20286770

Sold for a Sulphorus Grenadier's Softcap (4.5 buds w/ overpay)

http://www.tf2outpost.com/trade/15519995

Sold for a Miami Nights Tyrant's Helm (4.5 buds w/ overpay but the B/O was 3 buds)

http://www.tf2outpost.com/trade/19401782 -> http://backpack.tf/profiles/76561198063934288?time=1398236400

Sold for a Terror-Watt Buccaneer's Bicorne + Bill's Hat + 1 key + Strange Professional KS Black Box

http://puu.sh/9w5az/a764ae460d.jpg

Professional KS Black Box kits were selling for $45.23 which is 19 keys (1 bud at the time)

3.4 + .9 + .4 = 4.7 buds w/ overpay

http://www.tf2outpost.com/trade/19402915 -> http://www.tf2outpost.com/trade/19806887

Sold for an Eerie Orbiting Fire Hat With No Name (outdated)

There's a bunch of dupes on the market which can't be used as proof:

http://www.tf2outpost.com/trade/20030464

http://www.tf2outpost.com/trade/20359727

http://www.tf2outpost.com/trade/20367979

http://www.tf2outpost.com/trade/19385644

Rounding the range up to 4.5-4.7.