9 month old price!

Sale 1:

Sold for Steaming Executioner (3.5) [no overpay, hat was offered on]

http://www.tf2outpost.com/trade/25025192

Sale 2:

Sold for Sunbeams Larrikin Robin (3.65*0.9) = 3.285 (rounding to 3.3)

http://www.tf2outpost.com/trade/24980698

http://www.tf2outpost.com/item/440,3508230360,780,5 → http://www.tf2outpost.com/item/440,3508855232,314,5

Sale 3:

Sold for 3 buds + 3 keys (3/12) = 3 + 0.25 = 3.25 (rounding to 3.3)

http://www.tf2outpost.com/trade/25048828

http://backpack.tf/profiles/76561198067345147?time=1422691200

Sale 4: (outlier, sold within 2 hours)

Quicksold for 34 keys (34/12) = 2.83 (rounding to 2.8)

http://www.tf2outpost.com/trade/25035581 → http://backpack.tf/profiles/76561198075325715?time=1423728000

Sale 5: (outlier, sold fast and outdated hat)

Sold for Burning Buckaroo (~2.5 after overpay)

http://www.tf2outpost.com/trade/24979695 → http://backpack.tf/profiles/76561198066225875?time=1423382400

Notes:

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

http://www.tf2outpost.com/trade/25036747 - B/O of 38 keys (~3.2 buds)

Conclusion:

Sales at 3.5, 3.3, 3.3 and invalid sales at 2.8, 2.5. Due to the quicksale of 2.8 buds, taking a final range of 3.3-3.5 buds.

Feel free to support/counter my suggestion!

{requested by polar, credits to him for providing the sales)