Sale 1:

Sold for 8 keys + Pro. KS Collector’s Axtinguisher (~5)

No outpost

Seller: http://backpack.tf/profiles/76561198197516958#!/compare/1495411200/1495497600

Buyer: http://backpack.tf/profiles/76561198303645305#!/compare/1494374400/1495497600

X = 13

Sale 2:

Sold with ~3 keys in items for Kill-a-Watt Mann of Reason (14)

No outpost

Seller: http://backpack.tf/profiles/76561198201208967#!/compare/1493942400/1494028800

Buyer: http://backpack.tf/profiles/76561198296168912#!/compare/1493942400/1494028800

X = 11

Sale 3:

Sold for Bubbling Heavy Duty Rag (9.5) + 1 key

No outpost

Seller: http://backpack.tf/profiles/76561198119687405#!/compare/1493424000/1493596800

Buyer: http://backpack.tf/profiles/76561198089830691#!/compare/1493510400/1493596800

X = 11

Sale 4:

Sold for 10 keys in ~1-2 days

No outpost

Seller: http://backpack.tf/profiles/76561198263344996#!/compare/1494547200/1494633600

Buyer: http://backpack.tf/profiles/76561198345583271#!/compare/1494115200/1494633600

X = 10

Sale 5:

Sold for 8 keys + >0.5 keys in items in ~4 days

No outpost

Seller: http://backpack.tf/profiles/76561198296168912#!/compare/1494028800/1494374400

Buyer: http://backpack.tf/profiles/76561198336306929#!/compare/1494288000/1494374400

X = 9

Sale 6:

Quicksold for 9 keys

http://www.tf2outpost.com/trade/29185815 - B/O of 10

Seller: http://backpack.tf/profiles/76561198367837771#!/compare/1494979200/1495065600

Buyer: http://backpack.tf/profiles/76561198129564179#!/compare/1494979200/1495065600

X = 9

Sale 7:

Quicksold for Batsaber (9)

No outpost

Seller: http://backpack.tf/profiles/76561198136964833#!/compare/1493856000/1493942400

Buyer: http://backpack.tf/profiles/76561198201208967#!/compare/1493769600/1493942400

X = 9

Sale 8:

Quicksold for 8 keys + 13 ref (<0.5)

Seller: http://backpack.tf/profiles/76561198041902665#!/compare/1493769600/1493942400

Buyer: http://backpack.tf/profiles/76561198136964833#!/compare/1493856000/1493942400

X = 8

Sale 9:

Sold for 8 keys

http://www.tf2outpost.com/trade/29173470 - B/O of 9

Seller: http://backpack.tf/profiles/76561198091386392#!/compare/1494547200/1495152000

Buyer: http://backpack.tf/profiles/76561198300684734#!/compare/1494201600/1494979200

X = 8

Sale 10:

Sold with a couple keys worth of metal/ref for Steaming Stout Shako

Seller: http://backpack.tf/profiles/76561198195269186#!/compare/1494374400/1494460800

Buyer: http://backpack.tf/profiles/76561198091386392#!/compare/1494115200/1494460800

Should be used on the Shako.

Sale 11:

Bulk for Stormy Attendant

Seller: http://backpack.tf/profiles/76561198089830691#!/compare/1493596800/1493856000

Buyer: http://backpack.tf/profiles/76561198041902665#!/compare/1493769600/1493856000

Sale 12:

Bulk for Orbiting Planets Towering Pillar of Hats

Seller: http://backpack.tf/profiles/76561198290916628#!/compare/1494201600/1494460800

Buyer: http://backpack.tf/profiles/76561198263344996#!/compare/1494374400/1494460800

Sellers:

10 keys:

http://www.tf2outpost.com/trade/29222004 - 3 days

http://backpack.tf/u/76561198048635575

Sales at:

8 (2x)

9 (3x)

10

11 (2x)

13

Buyers at 8+ keys:

http://i.imgur.com/3vkATE1.png

Excluding 8.

13 looks like an outlier, and would most likely be lower if a B/O was present. Excluding 13.

9 may have quicksold a few times, but it sold far too often to be excluded. Keeping 9 in the range.

Going with 9-11.