Proof below

Clean only

Sales:

http://www.tf2outpost.com/trade/17530073

-wanted 13 buds

-sold for 9 buds+pink max+sf huntsman with parts+sf crossbow+sapper+shotgun+grenade+treasure hat=14 buds which is over the price of 13 buds

-seller's bp:

http://backpack.tf/id/76561198064242426?time=1390896000

http://backpack.tf/id/76561198064242426?time=1390982400 (max was already sold for extra bud+new keys)

http://www.tf2outpost.com/trade/16405053

-seems to have bought his for ge anger+pe tower+miami billy (unpriced but around 3): http://www.tf2outpost.com/trade/16348860 + http://www.tf2outpost.com/trade/16256637 + http://www.tf2outpost.com/trade/16256789

-can't use this but around 15 buds?

http://www.tf2outpost.com/trade/16956989

-wanted 13 buds

-sold for pe swagman+pe robin (both outdated)+3 buds+9 keys

-seller's bp:

http://backpack.tf/id/76561198047799762?time=1388649600

http://backpack.tf/id/76561198047799762?time=1388736000

-10.6 buds

http://www.tf2outpost.com/trade/16949878

-bought hearts ck+bazaar w/ parts: http://www.tf2outpost.com/trade/16474896 + http://www.tf2outpost.com/trade/16890049

-ck is 1 of 1 with no clear sales apart from that so looking at offers:

16 buds, a little bit fishy he didn't take it

sulph brainiac+hearts mining+8 keys=~12

misty grimme+stormy 13th ushanka=~12

ps anger could be around 15

http://www.tf2outpost.com/trade/17087943

-wanted 14 buds

-sold for duped burning trophy+steaming bonk (slightly outdated)+hearts aa+bmoc=~12.2 buds

-belt:

http://www.tf2outpost.com/trade/17087789

-sold for secret robin: http://www.tf2outpost.com/trade/17639001

-5.9 buds

http://www.tf2outpost.com/trade/17064132

-sold for stormy tc=5.9 buds

http://www.tf2outpost.com/trade/16823751

-wanted 20 buds

-sold for miami sensei (outdated but there are sales around 5.5)+bubbling jefe (2 before overpay)+searing hw (2.95 before overpay)+o.f. tossle=~11.4 buds

Current trades:

http://www.tf2outpost.com/trade/16695190

-wants 14 buds, 1 month

-notable offers:

terror muffs (outdated)=10.8

cloudy ballcap (year old price)=13.1

miami war pig (current price totally off now)

burning fruit+6 buds=13

c9 cannon+terror raincatcher (unpriced)=probably around 12

10 buds didn't take

surge exec (slightly outdated)=12.2

c9 antlers (outdated)=12.2

dp crones+roboactive panama (unpriced)=outlier?

c9 war pig (unpriced but ~13?)

cloudy ywn (year old price)+1 bud=14.5, above b/o and outlier

http://www.tf2outpost.com/trade/17622438

-b/o of 13 buds

-notable offers:

didn't take 10

http://www.tf2outpost.com/trade/13703819

-wants 14 buds, quite a few months now

-recent notable offers:

rejected 10 buds

Sales: 10.6, 11.4, 12.2, 13

Asked polar about this, 11.5 should be the low end. I think 12 would work too but can't disprove 11.5 with the sale around there. Anything below seems low. 13 is obviously the high end.