===UPDATE===

(Note: "===" is update)

Just noticed this is a raise since my suggested price is going above the mean of the current range.

Sellers SALES at 15 ref:

=== http://www.tf2outpost.com/trade/26412986

^^^^^

http://www.tf2outpost.com/item/440,3921623172,6020,6 (no longer in seller's inventory)

http://backpack.tf/item/3921623172 (new owner after the seller)

=== http://www.tf2outpost.com/trade/26412460

^^^^^

http://www.tf2outpost.com/item/440,3916954406,6020,6 (no longer in seller's inventory and new owner)

Unsolds at 1 key:

=== http://www.tf2outpost.com/trade/26386058 - 5 days

http://www.tf2outpost.com/trade/26321688 - 1 week

http://www.tf2outpost.com/trade/26332228 - 1 week

http://www.tf2outpost.com/trade/26320023 - 1 week

http://www.tf2outpost.com/trade/25993110 - 1 month

http://bazaar.tf/trade/1289119 - 2 month

http://bazaar.tf/trade/1246068 - 3 month (that 1 wasn't sold, disappeared without a new owner: http://backpack.tf/item/1551058326 )

Unsolds at 18 ref:

=== http://www.tf2outpost.com/trade/26415115 - 2 days

http://www.tf2outpost.com/trade/26105173 - Unsold at 18 ref - 1 month

^^^

http://www.tf2outpost.com/item/440,3783317409,6020,6 & http://backpack.tf/item/881880106

(inb4 people tell me it was "sold", check the history; it was last seen by the seller before disappearing. Can't confirm it was sold).

Conclusion:

There are now sales at 15 ref, which is higher than the low-end and the medium of the current price range. Also, there are unsolds at 1 key, showing that the high-end should be removed. The unsolds at 18 ref unsolds help support that anything higher than 15 ref is unsuccessful.

I will continue to update if there are more evidence available.

Support, counter, feedback is always helpful~