I went to NAPA yesterday to get an oil filter for my home backup generator and asked about a case price (12 filters). He sold me the one I needed for the oil change and told me to come back on either of the last two days of the month to save money when all filters are 40% off. He said they do this every month. I don't know if this is only the local NAPA dealer but it might be worth asking your local NAPA dealer about discounts.
Bob, Sandi & Marmaduke the Big Pug and Tasha a Frenchie
SW OREGON Winnebago Outlook Ford V-10
If towing: a 2006 Mini Cooper or 2015 RAM Limited 4X4 or a 86 El Camino on a trailer