Sale 1:

Sold for Bubbling Festive Tree (19)

No outpost

Seller: http://backpack.tf/profiles/76561198119629032#!/compare/1479859200/1479945600

Buyer: http://backpack.tf/profiles/76561198069297901#!/compare/1479945600/1480118400

X = 19

Sale 2:

Sold for 18 keys

No outpost

Seller: http://backpack.tf/profiles/76561198344933095#!/compare/1483574400/1483660800

Buyer: http://backpack.tf/profiles/76561198085370004#!/compare/1483660800/1483747200

X = 18

Sale 3:

Quicksold for 15 keys

http://www.tf2outpost.com/trade/28635536 - B/O of 17

Seller: http://backpack.tf/profiles/76561198069297901#!/compare/1480377600/1480464000

Buyer: http://backpack.tf/profiles/76561198128005244#!/compare/1480377600/1480464000

X = 15

Sale 4:

Sold for Aces High Fruit Shoot

No outpost

Seller: http://backpack.tf/profiles/76561198192375733#!/compare/1481932800/1482364800

Buyer: http://backpack.tf/profiles/76561198144976976#!/compare/1481846400/1482019200

This’ll end up being way too low.

Sellers:

17 keys:

http://i.imgur.com/orUbMkc.png

http://backpack.tf/u/76561198155659357

http://www.tf2outpost.com/trade/28775569 - young

18 keys:

http://i.imgur.com/jvUjvhx.png - 14 days

http://backpack.tf/u/76561198344933095

19 keys:

http://i.imgur.com/LHvCQEz.png - 15 days

http://backpack.tf/u/76561198192602363

http://www.tf2outpost.com/trade/28770586

http://i.imgur.com/siwoPzY.png - 2 months

http://backpack.tf/u/76561198006544512

http://www.tf2outpost.com/trade/28682531

http://i.imgur.com/ihZ3krt.png - 29 days

http://backpack.tf/u/76561198164651434

http://www.tf2outpost.com/trade/28748497

http://www.tf2outpost.com/trade/28766126 - 5 days

http://backpack.tf/u/76561197963104085

25 keys:

http://i.imgur.com/Kl73brv.png

http://backpack.tf/u/76561198009549726

Sales at:

15

18

19

15 quicksold, and is countered by buyers. Excluding 15.

Going with 18-19.