Sale 1:

Sold for Steaming Private Eye (15) + ~3 keys in items

No outpost

Seller: http://backpack.tf/profiles/76561197960328421#!/compare/1467936000/1468022400

Buyer: http://backpack.tf/profiles/76561198190503265#!/compare/1467936000/1468022400

X = 18

Sale 2:

Sold for 10 keys + ~5 keys in items

No outpost

Seller: http://backpack.tf/profiles/76561198078298306#!/compare/1463875200/1463961600

Buyer: http://backpack.tf/profiles/76561198142784188#!/compare/1463875200/1463961600

X = 15

Sale 3:

Sold for Kill-a-Watt Scotch Bonnet (Mini at 12 below) + 1 key + White Bandana (1)

No outpost

Seller: http://backpack.tf/profiles/76561198142784188#!/compare/1465516800/1465689600

Buyer: http://backpack.tf/profiles/76561198057968550#!/compare/1465603200/1466035200

X = 14

Sale 4:

Quicksold for 13 keys

No outpost

Seller: http://backpack.tf/profiles/76561198068180717#!/compare/1468972800/1469059200

Buyer: http://backpack.tf/profiles/76561198115002067#!/compare/1468454400/1469059200

X = 13

Sale 5:

Quicksold for 12 keys

http://www.tf2outpost.com/trade/28337266 - Deleted B/O, Seller confirms sale

Seller: http://backpack.tf/profiles/76561198068235514#!/compare/1468627200/1468800000

Buyer: http://backpack.tf/profiles/76561198145194305#!/compare/1468713600/1468800000

X = 12

Sale 6:

Sold for Strange Pro. KS Festive Grenade Launcher (11)

http://www.tf2outpost.com/trade/28276445 - B/O of 15

Seller: http://backpack.tf/profiles/76561198083968668#!/compare/1467072000/1467331200

Buyer: http://backpack.tf/profiles/76561198135606151#!/compare/1467331200/1467417600

X = 11

No current sellers

Scotch Bonnet Mini:

Sold for 10 keys + ~2 keys in items in less than a day

http://www.tf2outpost.com/trade/28346249 - B/O of 12

Seller: http://backpack.tf/profiles/76561198046191142#!/compare/1468713600/1468800000

Buyer: http://backpack.tf/profiles/76561198067645241#!/compare/1468627200/1468800000

X = 12

Sales at:

11

12

13

14

15

18

Sales at 13 and less sold too quickly to be included in the range. An offer of a Bubbling Fukaamigasa + 2 keys was also made, according to the outpost trade of sale 6, which could easily achieve at least 13 keys. Excluding 13 and below.

Going to call 18 an outlier due to the amount of sales for less

Going with 14-15