Proof below (3 sales). Overpay is applied.

Prices used are of time of sale.

1st sale:

http://www.tf2outpost.com/trade/13561249 bought stormy cosa and 18 keys here: http://www.tf2outpost.com/trade/13844966 =~3.2 buds

2nd sale:

http://www.tf2outpost.com/trade/13390253 added bud and bills to buy ghosts cosa=~3.1 buds

3rd sale (2 months old):

http://www.tf2outpost.com/trade/12021986 sold between 115 to 130 usd paypal and taking buds as 40, =~2.9 to 3.3 buds. Average=3.1 buds

Sales: 3.1, 3.1, 3.2

All 3 sales are within the suggested range.