how about another sale then ?

Sale #1:

http://www.tf2outpost.com/trade/26057173 Sold for Blizz Stuntman + 1 key in sweets

B/O for Bonnet was 14

Stuntman had no trade, presuming offered

X = 1*0.9 + 13*0.9

X = 13

Stunt https://backpack.tf/item/511230120

Bonnet https://backpack.tf/item/2176702392

Mini for Stuntman

Courtesy of Stealth for the sale

Sold for blizz gym rat:

http://backpack.tf/item/1121336012

http://backpack.tf/item/1773987070

Sale #2:

sold for an OC bomber*

http://www.tf2outpost.com/item/440,3844186084,306,5 > http://backpack.tf/item/1668633722

* mini on bomber http://backpack.tf/item/1668633722 > http://backpack.tf/item/3331168295

23 * 0.9 = 21. b/o was 13 - and it sold in a day

Sale #3:

http://www.tf2outpost.com/item/440,3844186064,255,5 > http://www.tf2outpost.com/item/440,3844186084,306,5

sold for a miami stuntman* = 15

stuntman mini:

http://www.tf2outpost.com/trade/26260658 - sold for an o. fire sultans* + TS bills (histories are good on the bills + sultans,but the stunt skipped an owner. proof of the trade - http://prntscr.com/7makg6) 16.5~

http://www.tf2outpost.com/trade/25689651 - sold for 3 buds in 2 days~ 15 keys

sultans mini:

http://www.tf2outpost.com/item/440,3829355267,403,5 > http://www.tf2outpost.com/item/440,3883924455,780,5

sold for a bubbling fedora 16 * 0.9 = 14.4

Quicksell #1 (outlier):

http://www.tf2outpost.com/trade/26004417 Sold for 11 keys to a quickbuyer

http://www.tf2outpost.com/trade/26088230

Keys http://gyazo.com/2e5f92fb5fda7ada1fd438f19dfbc6a2

Bonnet https://backpack.tf/item/2203288407

further proof why 11 is an outlier:

http://www.tf2outpost.com/trade/26222200 - declined 11

summary:

11,13,13(had an offer of 12),15

11 is a quicksell,it sold to a quickbuyer.it's obvious that the hat can get higher than 11.i personally can't get it for 11. there are 3 sales higher than 11.