Only 2 sales in the past 3 months, so I'm gonna use both of them here.

http://www.tf2outpost.com/trade/19335005 - Sold for a Searing Plasma (non-robo) Baker Boy (2.7 * 0.9 = 2.43 rounded to 2.4) + Professional Killstreak S.F. Scattergun (3.4 * 0.9 = 3.06 rounded to 3.1 buds, see below). 5.5 buds.

http://www.tf2outpost.com/trade/19373769 - Sold for a Haunted Ghosts Demoman's Fro (2.5 * 0.9 = 2.25 rounded to 2.3) + DBD Robo Capotain (1.6 * 0.9 = 1.44 rounded to 1.4) + 43 keys (+ sweets?), which was worth about 2.2 buds at the time. 5.9 buds.

The Pro KS S.F. Scatter is valued at 3.4, because the approximate worth of one on the Steam Market right now (back then) is/was about 12 keys more than the normal one. Add in an extra key or two because of the strange parts and that amounts to 13.5 keys. Buds were worth 19 keys at the time of the sale, so that means about .7 buds can be added onto the item's price.