re-suggesting, not sure if im right.

sale 1: sold with 1 key of sweets for stormy baker[21 keys]

http://backpack.tf/profiles/76561198077958763?time=1424160000

http://backpack.tf/profiles/76561198077958763?time=1428735600

21*0.9=18.9 rounding to 19

19-1=18

sale 2: sold for smoking elfin[12 keys]

http://backpack.tf/profiles/76561198051032766?time=1434351600

http://backpack.tf/profiles/76561198051032766?time=1434438000

12*0.9=10.8 rounding to 11

sale 3: sold with duped beams jeepcap for shadows snaggle+8 keys

http://backpack.tf/profiles/76561198149180255?time=1433833200

http://backpack.tf/profiles/76561198149180255?time=1434178800

not using.

sale 4: in a deal with 3 other hats for beams bone dome

http://backpack.tf/profiles/76561198149180255?time=1433660400

http://backpack.tf/profiles/76561198149180255?time=1433746800

sale 5: another bulk deal

http://backpack.tf/profiles/76561198092593904?time=1433401200

http://backpack.tf/profiles/76561198092593904?time=1433487600

sale 6: sold with a key for bubbling voodoo[16.5 keys]

http://backpack.tf/profiles/76561198058691137?time=1431673200

http://backpack.tf/profiles/76561198058691137?time=1432191600

16.5*0.9=14.85 rounding to 15

15-1=14

sale 7: sold for stormy sola topi[10 via mini]

http://backpack.tf/profiles/76561198107629050?time=1430895600

http://backpack.tf/profiles/76561198107629050?time=1430982000

mini on topi: sold for bubbles capos capper[11 keys]

http://backpack.tf/profiles/76561198090590975?time=1429599600

http://backpack.tf/profiles/76561198090590975?time=1430118000

11*0.9=9.9 rounding to 10

offer of 15 keys on this hat: http://www.tf2outpost.com/trade/25672698

sales at 10, 11, 14 and 18. 15 shows 10 and 11 are low. and 3v1lc says his sale is around 14-18: http://backpack.tf/vote/id/558c4319dea9e9f53f8b47c6

so taking a final price of 14-18 keys.