Proof below. Surprised this goes below 10.

Sales:

http://www.tf2outpost.com/trade/14801016

-wanted 15 buds

-sold for roboactive hotrod (outdated)+electrostatic brainiac=10.8 buds

-notable offers:

lantern wraith+sweets=8.9+

miami sam=9.6

http://www.tf2outpost.com/trade/14310239

-owner at the time also had a v. big kill where the eventual buyer of the c9 cannonball offered his disco bubble, but in the end the c9 cannonball sold for the bubble

http://backpack.tf/id/76561198027603870?time=1380783600

http://backpack.tf/id/76561198027603870?time=1380870000

-10.1 buds

http://www.tf2outpost.com/trade/14585035

-b/o of 15 buds

-sold/bought for the duped v. big kill seen above: http://www.tf2outpost.com/trade/14310239

-no notable offers

http://www.tf2outpost.com/trade/15413233

-sold for 10 buds like he wanted

-no notable offers

http://www.tf2outpost.com/trade/14660446

-b/o of 15 buds on another trade: http://www.tf2outpost.com/trade/14720275

-cannonball+blizz scotch bonnet sold for c9 chapeau+planets bonk boy (alt acc offered): http://www.tf2outpost.com/trade/14020734

-~6.3 buds, outlier

-no notable offers on both trades

http://www.tf2outpost.com/trade/14640902

-kaw hoc+secret dixie+logo beanie (1.3 outdated)+nnb billycock seem to have sold for the c9 cannonball above this sale

-10.7 buds

http://www.tf2outpost.com/trade/14550226

-'quickselling' for 12 buds on another trade

-sold for kaw cosa+6 buds=~9.1 buds

-apparent notable offers:

hearts reggae+ghosts fez=10.1

http://www.tf2outpost.com/trade/14435944

-valued it at 7-9 buds?

-cannonball+pe football helm bought ghosts modest: http://www.tf2outpost.com/trade/14503879

-8.6 buds, no overpay as offered

-notable offers:

cauldron modest=13.5 (year old price, way too old to be trusted and also wasn't offered on the trade)

http://www.tf2outpost.com/trade/14217788

-b/o of 17 buds

-bought miami wraith: http://www.tf2outpost.com/trade/14303718

-~10.1 buds, no overpay as offered

-notable offers:

cloudy bicorne=10.6

electrostatic das gute (looks severely overpriced)+a aces antlers=11.6, close enough

-offers from older trade: http://www.tf2outpost.com/trade/13878270

cloudy waxy=10.4

duped burning bicorne if seller adds a bit=9-10?

c9 anger+3 buds=10.5

misty brainiac=9.7

apparent offer of burning front runner (outdated)+hearts marauder if seller adds 2 buds, never offered on trade, could be duped

Current trades:

http://www.tf2outpost.com/trade/15194155

-b/o of 18-20 buds in unusuals

-sold for kaw modest (got it for the duped tyrantium)+vivid phantom=? modest is unpriced

-no notable offers

http://www.tf2outpost.com/trade/13477527

-b/o of 18 buds, 4 months

-notable offers:

miami modest scrap (unpriced but around 10)

http://www.tf2outpost.com/trade/16157005

-wants 14 buds, no offers

http://www.tf2outpost.com/trade/16173612

-wants 15 buds, no offers

http://www.tf2outpost.com/trade/15676004

-b/o of 28 buds, 1 month

-notable offers:

aces hoc (unpriced though)

http://www.tf2outpost.com/trade/16025245

-b/o of 28 buds, 1 week

-notable offers:

disco tyrantium (unpriced but over 10?)

Sales: 6.3, 8.6, 9.1, 10, 10.1, 10.1, 10.7, 10.8

For low end, there are 2 sales ~9 and they didn't sell quickly so I'm including them. High end is from 2 sales ~11. Most notable offers also seem to be around this range so this looks good. Unusual overpay and original prices used.