Proof below. 4 month-old price.

This is actually an increase from original suggested value of 8-10.

Cleans only, correct me if I'm wrong.

Sales:

-brigade+blizz head warmer, bought burning head warmer (13.25): http://www.tf2outpost.com/trade/15252836

-9 buds, no overpay as offered

http://www.tf2outpost.com/trade/15769325 + http://www.tf2outpost.com/trade/15138119

-sold/bought tw robo glove (unpriced)+ge swagman+hearts trilby for his scorching brigade: http://www.tf2outpost.com/trade/15912900

http://www.tf2outpost.com/trade/15596646

-'quickselling' for 9 buds

-brigade+1 bud sold for clean houwar

-buyer's bp:

http://backpack.tf/id/76561198047941920?time=1384070400

http://backpack.tf/id/76561198047941920?time=1384156800

-9 buds, not counting overpay on clean houwar

http://www.tf2outpost.com/trade/15569893

-brigade+beams mullet+ghosts sam bought terror watt cone (unpriced): http://www.tf2outpost.com/trade/15572517

http://www.tf2outpost.com/trade/15698095

-b/o of 15 buds

-bought burning lid: http://www.tf2outpost.com/trade/15568645

-9.7 buds, no overpay as offered

http://www.tf2outpost.com/trade/14942381

-sold for duped burning noble (clean was 9.25 without overpay)+2 buds+2 keys

-seller's bp:

http://backpack.tf/id/76561197998127300?time=1382166000

http://backpack.tf/id/76561197998127300?time=1382252400 (don't knew where buds were)

-~9.5 buds, considering duped as 1 bud less like the seller

http://www.tf2outpost.com/trade/15896561

-b/o of 13 buds

-brigade+duped 13th hour fro (3.3) bought (duped) v. community luger (seller doesn't seem to have added anything)

-luger: http://www.tf2outpost.com/trade/15798879

-seller's bp:

http://backpack.tf/id/76561198016049778?time=1385107200

http://backpack.tf/id/76561198016049778?time=1385193600

-duped sparkle lugers are ~12 according to polar

-~8.7 buds, but the luger isn't great to base the low end off. regardless this is still ~9

http://www.tf2outpost.com/trade/14489444

-wanted 10 buds

-sold for 7 buds+beams cone (2.2 outdated)

-~9.2 buds

http://www.tf2outpost.com/trade/13913099

-old

-sold for beams attendant (newer suggestion probably more accurate than old one, 10-11 before overpay)+#55 breather bag+45 whiskered gentlemen=10 buds

-seller's bp:

http://backpack.tf/id/76561198050247262?time=1378018800

http://backpack.tf/id/76561198050247262?time=1378105200

Current trades:

http://www.tf2outpost.com/trade/15959726

-notable offers:

ghosts modest=9.4

http://www.tf2outpost.com/trade/15206735

-b/o of 14 buds, more than a month

-notable offers:

burning birdcage (never properly priced)+1 bud=10.8, can't use this

duped scorching front runner (year old price)+2 buds=10-11?, can't use this

ghosts modest (offered above)=9.4

http://www.tf2outpost.com/trade/15715615

-wants 13-14 buds

-notable offers:

beams aa+hearts fuka (outdated)=9.7

http://www.tf2outpost.com/trade/15917774

-wants 12 buds

-notable offers:

ghosts modest (offered above)=9.7

clean lantern stahl+nnb dappers+headcase=10.7

http://www.tf2outpost.com/trade/14787346

-wants 11 buds, almost 2 months

-notable offers:

burning birdcage (never priced)+2.5 buds=12.3, bud above what he has wanted for 2 months, obvious outlier

disco chapeau=9.5

duped burning phantom+sf sticky=around 10 buds or less

sulph flamenco+15 keys=10.3

harvest marauder=9

blizz crone+2 buds=9.2

duped burning noble (same one as above sale)+vivid snaggle=9.1

ge pyromancer+gbh firewall=10

duped scorching front runner (year old price)+3 buds=11-12?

c9 bubble+p. fetti glengarry (not purple fetti)=9.2

a.f. brigade+g. fetti lucha (outdated) if seller adds planets kabuto (1.2 outdated)=9.2

aces gibus if seller adds 0.5=10.3

misty chapeau=9.2

eerie tower+ghosts noble=9.4

ghosts bubble+5 buds=10.4

cloudy merry (outdated)+1.5=9.4

Sales: 8.7, 9, 9, 9.2, 9.5, 9.7, 10

Going with a nice simple range here of 9-10, most offers are between this range as I have proved above. The 2 offers at ~11 are all involving hats with outdated prices, don't think they're usable but definitely shouldn't be included in the range. Unusual overpay and original prices used when necessary.