Sale 1:

Sold for 16 keys

http://www.tf2outpost.com/trade/28119801 - No B/O

Seller: http://backpack.tf/profiles/76561198112281935#!/compare/1462320000/1462406400

Buyer: http://backpack.tf/profiles/76561198271192883#!/compare/1462147200/1462492800

X = 16

Sale 2:

Sold for 17 keys

http://www.tf2outpost.com/trade/28143928 - B/O of 18

Seller: http://backpack.tf/profiles/76561198271192883#!/compare/1463011200/1463270400

Buyer: http://backpack.tf/profiles/76561198043992035#!/compare/1463097600/1463184000

X = 17

Sale 3:

Sold for Kill-a-Watt Whirly Warrior + a 2 key rocket launcher skin

No outpost

Seller: http://backpack.tf/profiles/76561198043992035#!/compare/1463616000/1463702400

Buyer: http://backpack.tf/profiles/76561198233331152#!/compare/1463616000/1463702400

Looking into the Whirly Warrior, I could only find one usable sale, that would bring its value to around 25 keys. I’d be willing to call this sale here an outlier.

Whirly Warrior:

Sold for Logo Milkman + ~6 keys in botkillers

http://www.tf2outpost.com/trade/28111951 - Deleted B/O -_-

Seller: http://backpack.tf/profiles/76561198088878793#!/compare/1461974400/1462060800

Buyer: http://backpack.tf/profiles/76561198233331152#!/compare/1461974400/1462060800

X = ~25?

Sales at:

16

17

Going with 16-17