Just to be clear, I didn't mean to buy the cheap filters off ebay. I only buy the OEM Motorcraft period. They are a little cheaper than Advance if you buy 2 sets. Advance runs about 50 bucks with tax. These are $41 each with shipping.
eBay Motors: Ford Powerstroke 6.0 Diesel Fuel Filter 2x OE F350 F450 (item 270271201525 end time Sep-10-08 18:19:10 PDT)
If you watch the auctions, you can even get them for a little less. I picked up a set for $33 once, but you generally have to bid to get them that cheap. I've never seen a buy it now much cheaper than 40-45 shipped.