Since no one made a counter suggestion…

http://puu.sh/6BmHi/a7dfddb9ff.png

SOLD: 1 bud + 57 keys (3.9 buds)

http://www.tf2outpost.com/trade/17679304

SOLD: Australium Sniper Rifle (2.5-3.0) + 1 bud + 4 keys

(3.7-4.0 buds)

http://i.imgur.com/jpO5Fjx.png

SOLD: Burning Ze Goggles (3.8 buds w/ overpay)

http://puu.sh/6J5nm.png

SOLD: 4 buds

http://www.tf2outpost.com/trade/16839017

-Involved in a trade for Caribou

SOLD: GE Cosa Nostra + 5 keys

(3.8 buds w/ overpay)

http://www.tf2outpost.com/trade/17645865 (SOLD EXTREMELY QUICKLY)

SOLD: apparently 65 keys

http://www.tf2outpost.com/trade/17001621 (SOLD EXTREMELY QUICKLY)

SOLD: Bubbles Team Captian (3.3 buds w/ overpay)

http://www.tf2outpost.com/trade/17015769

-apparently a C/O of 3 buds

Offers:

-70 keys (3.6 buds)

http://www.tf2outpost.com/trade/16972877

same guy who offered above could go 80 keys (4.1 buds)

http://www.tf2outpost.com/trade/17577309

This is the trade where the guy above has bought his from. We can then assume he bought within the 70-80 key range.

http://backpack.tf/profiles/76561198055454282

-within this time, he lost 80 unique items. therefore, he could have paid 80 keys, being a sale of 4.1

Looking over the 3.0 - 3.3 sales, most sold within half a day. Very quick for a high value item.

Buyout on the classies for 4 buds, while it is certainly possible to get 4 buds. So the high end shall be that.

3.6 buds went a bit quickly in my opinion, so 3.8 buds (next lowest stable value) shall be the low end.