Sale 1:

Sold for 5 buds + 4 keys (4/12) = 5 + 0.33 = 5.33 (rounding to 5.3 buds)

http://www.tf2outpost.com/trade/24958543

Sale 2:

Involved in a bulk deal for a Golden Pan

http://backpack.tf/profiles/76561197973509105?time=1425369600 → http://backpack.tf/profiles/76561197973509105?time=1425542400

Sale 3: (outlier, sold within 3 hours)

Sold for 55 keys (55/12) = 4.58 (rounding to 4.6 buds)

http://www.tf2outpost.com/trade/25281025

http://i.imgur.com/6tUCA4G.png

Sale 4:

Involved in a complex deal

http://backpack.tf/profiles/76561198039620591?time=1421222400 → http://backpack.tf/profiles/76561198039620591?time=1420704000

Sale 5: (seller was a pretty inexperienced trader)

Sold for 4 buds + 6 keys (6/12) = 4 + 0.5 = 4.5 buds

http://www.tf2outpost.com/trade/25158089

http://backpack.tf/profiles/76561198044611776?time=1424592000 → http://backpack.tf/profiles/76561198044611776?time=1424764800

Sale 6:

Sold for 80 keys (80/12) = 6.67 (rounding to 6.7 buds)

http://www.tf2outpost.com/trade/25002984

Sale 7:

Sold for 80 keys (80/14) = 5.71 (rounding to 5.7 buds)

http://www.tf2outpost.com/trade/24666226

http://backpack.tf/profiles/76561198036591954?time=1422072350 → http://backpack.tf/profiles/76561198036591954?time=1422086400

Support-proof:

http://www.tf2outpost.com/trade/24926663 - Declined an offer of 2 Max's Heads (~6.5 buds)

http://www.tf2outpost.com/trade/24926663 - Declined an offer of 6 buds

http://www.tf2outpost.com/trade/24077507 - Declined two offers of 6 buds

http://www.tf2outpost.com/trade/24077507 - Not accepting anything under 7 buds

Notes:

For valuing the buds, I'm using the price at the time of sale.

All sales from the previous accepted suggestion are now outdated or close to being outdated; thus using more recent sales.

Conclusion:

Sales at 5.3, 6.7, 5.7 and quicksales at 4.5, 4.6 buds, along with the plenty of support-proof suggesting that this taunt is close to or even more than the 6 buds region.

Thus, taking a final range of 5.7-6.7 buds.

Feel free to support/counter my suggestion!