Very hard to sell at 4 keys and people are selling at 3-3.5 keys. Proof in comments

Selling at 3 keys:

http://www.tf2outpost.com/trade/8328395

http://www.tf2outpost.com/trade/7963612

http://www.tf2outpost.com/trade/8021648

http://www.tf2outpost.com/trade/8182636

Selling at 3.5 keys:

http://www.tf2outpost.com/trade/8282119

http://www.tf2outpost.com/trade/8236520

Unsold at 4 keys:

http://www.tf2outpost.com/trade/8269746 - 3 days

http://www.tf2outpost.com/trade/8265759 - 4 days

http://www.tf2outpost.com/trade/8067106 - 1 week

http://www.tf2outpost.com/trade/8136301 - 1 week

http://www.tf2outpost.com/trade/8291013 - 2 days

http://www.tf2outpost.com/trade/8267889 - 3 days

http://www.tf2outpost.com/trade/8264815 - 3 days

http://www.tf2outpost.com/trade/6929034 - 1 month!

http://www.tf2outpost.com/trade/8101706 - 1 week

http://www.tf2outpost.com/trade/8205187 - 5 days

http://www.tf2outpost.com/trade/8320291 - 1 week

http://www.tf2outpost.com/trade/7695229 - 3 weeks

http://www.tf2outpost.com/trade/8160569 - 6 days

3-3.5 keys offers:

http://www.tf2outpost.com/trade/6128594 http://www.tf2outpost.com/trade/6398363 - accepted at 3.5 http://www.tf2outpost.com/trade/7288202 http://www.tf2outpost.com/trade/8126624 http://www.tf2outpost.com/trade/7991533 -accepted at 3.5

Bought Widowmakers:

http://www.tf2outpost.com/trade/8314684 - Bought 1 for 3.5 keys

http://www.tf2outpost.com/trade/8295520 - bought 6 @ 3 keys each