rockauto.com has the K&N HP-4005 oil filter that fits the Ford 6.7L powerstroke diesel on closeout for $3.94. Shipping is dependent on location but for my area I could get up to 12 shipped for $6.99
total price for me is $54.27 / 12 = $4.52 each shipped
Typical price for these is about $20 each. Slickdeal for the DIY crowd.
At the time of posting, there are 116 available.
update: 7236093164150674 in referral box for 5% off, down to 80 left