9 month old price!

Sale 1:

Sold with 1 bud for Haunted Ghosts Killer's Kabuto

X + 1 = 5 (no overpay, was offered on)

X = 4

http://www.tf2outpost.com/trade/24782182

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

Sale 2:

Sold for 51 keys (51/14.5) + Strange Professional Original* (10/14.5) = 3.52 + 0.69 = 4.21 (rounding to 4.2)

http://www.tf2outpost.com/trade/24292543

Sale 3: (bulk deal, complex sale)

Sold with Stormy Bonk Boy + DBD Wet Works + Sweets for Burning Hermes

http://www.tf2outpost.com/trade/24172410

http://backpack.tf/profiles/76561198097798693?time=1418877563 → http://backpack.tf/profiles/76561198097798693?time=1418889600

Sale 4:

Sold for 4 buds pure

http://www.tf2outpost.com/trade/23798402

Mini for Strange Professional Original*: (after tax)

~$23.90 = ~9.96 keys

~$22.38 = ~9.33 keys

~$25.65 = ~10.69 keys

~$24.36 = ~10.15 keys

~$22.93 = ~9.55 keys

~$26.08 = ~10.87 keys

~$25.66 = ~10.69 keys

~$25.59 = ~10.66 keys

Valuing this at ~10 keys.

Notes:

http://www.tf2outpost.com/trade/24806153 - offer of 4 buds pure

Conclusion:

Sales at 4, 4.2, 4. Taking final range of 4-4.2 buds.

Feel free to support/counter my suggestion!