Still seems a tad high, but there are no lower sellers/sales as far as I know.

Sale or 4 keys

https://i.gyazo.com/0957635a081737350584a840083e9185.png

Classifieds Sellers

https://i.gyazo.com/e11b23564082c58ae8841c7dccc288b3.png

http://backpack.tf/item/4916577935 - 4 keys / 1 day

http://backpack.tf/item/4969092003 - 4 keys / 12 hours

http://backpack.tf/item/4814534461 - 4 keys / 2 days

http://backpack.tf/item/5158526271 - ~4 keys / 1 day

http://backpack.tf/item/4942997465 - ~5.5 keys (lol, good luck) / 14 days

Outpost Sellers

http://www.tf2outpost.com/trade/28542391 - 4 keys / 10 hours / quicksold (the one I bought)

http://www.tf2outpost.com/trade/28540765 - 4 keys / 1 day

http://www.tf2outpost.com/trade/28524702 - 4.5 keys / 1 week

SCM is a little weird since there are 5 sellers for around 3.5 keys, but there are still a couple of fairly recent sales up to 5 keys.

http://steamcommunity.com/market/listings/440/Strange%20Dad%20Duds

I'll just see where this one goes. 4 keys is at least the most common trading point outside of SCM.