Sale 1:

Sold for Orbiting Fire Private Eye (17) + 3 keys

No B/O in sight

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1498521600/1498608000

Buyer: https://backpack.tf/profiles/76561198117598946#!/compare/1498262400/1500163200

X = 20

Sale 2:

Sold for Morning Glory Bootleg Base Metal Billycock (Mini at 18 below) + 1 key

http://www.tf2outpost.com/trade/29267975 - B/O of 20

Seller: https://backpack.tf/profiles/76561198156255538#!/compare/1499904000/1499990400

Buyer: https://backpack.tf/profiles/76561198129116317#!/compare/1499904000/1499990400

X = 19

Sale 3:

Quicksold for 16 keys

http://www.tf2outpost.com/trade/29294608 - B/O of 16

Seller: https://backpack.tf/profiles/76561198129116317#!/compare/1501027200/1501200000

Buyer: https://backpack.tf/profiles/76561198068654532#!/compare/1501027200/1501200000

X = 16

Sale 4:

Sold for much more than 16 keys worth in unsuals/items

http://www.tf2outpost.com/trade/29294608 - B/O of 16

Seller: https://backpack.tf/profiles/76561198129116317#!/compare/1499990400/1500163200

Buyer: https://backpack.tf/profiles/76561198336846247#!/compare/1500076800/1500163200

X = 16 (Capped by B/O)

Morning Glory Bootleg Base Metal Billycock Mini:

Sold for 18 keys

http://www.tf2outpost.com/trade/29332442 - B/O of 18

Seller: https://backpack.tf/profiles/76561198081172172#!/compare/1503705600/1503792000

Buyer: https://backpack.tf/profiles/76561198152618612#!/compare/1503705600/1503792000

Sellers:

16 keys:

http://www.tf2outpost.com/trade/29294730 - 1 month

http://webcache.googleusercontent.com/search?q=cache:_KvQZS83V_sJ:www.tf2outpost.com/trade/29294730+&cd=1&hl=en&ct=clnk&gl=au

http://i.imgur.com/wwl2CE8.png - was lowered sometime in the last few days

Sales at:

16 (2x)

20

Ignoring the quicksell at 16, due to the current seller at 16.

Going with 16-20.