Third try. I hope it's correctly now. 12 exist.

Sellers:

http://www.tf2outpost.com/trade/23315542 20 keys

http://www.tf2outpost.com/trade/24729185 1.3 buds

http://www.tf2outpost.com/trade/24726417 asking 2 buds, no offers so far

Solds:

http://www.tf2outpost.com/trade/24314198 b/o 20 keys, unclear for what it sold

http://www.tf2outpost.com/trade/24001337

5 keys were added for the headset

http://backpack.tf/profiles/76561198107981246?time=1420444800

b/o of 19 keys here http://www.tf2outpost.com/trade/24435178 ~1.3 buds.

Overpay included ~1.5 buds.

http://www.tf2outpost.com/trade/23910705 Sold for 19 keys.

More recent sales.

http://www.tf2outpost.com/trade/24330639 Sold for Miami Nights Counterfeit Billycock(1.5 buds outdated)

Miami Nights Counterfeit billycock

http://www.tf2outpost.com/trade/24362308 b/o 20 keys (~1.4 buds)

http://www.tf2outpost.com/trade/24690722

Sold for Bubbling Tam O' Shanter(14.5 keys * 0.9 = ~13 keys)

+ Dead Presidents Shooter's Sola Topi(14.5 keys * 0.9 = ~13 keys).

Making this ~1.7 buds but b/o is 1.5 buds. Taking =1.5 buds

A range of 1.4-1.5 buds. Taking 1.45 buds as mini suggestion price.

With 1.45 buds * 0.9 = ~1.3 buds.

Credits for proof to aaroncsn. Thanks for your help.

http://backpack.tf/vote/id/54ab141ab98d88f73d8b4719