On all of the models in the Apple Store, most additions will raise the ship time to "1-3 business days", but ONLY the 500GB hard drive raises the ship time to either 3-5 days (17" and 20" models) or 5-7 days (24" model). None of the other hard drive options cause this issue. The 500GB drive (not sure if it's the same model) does not cause any greater delay on the Mac Pro. Any idea why this might be?