Amazon.com offers this Post Raisin Bran Cereal 47-oz. Box 2-Pack
for $9.91. Order via Subscribe & Save and it falls to $8.42
with free shipping
. At $4.21 per box, that's $15 off and the lowest total price we could find for this cereal in this quantity.
Of note, be sure to cancel Subscribe & Save after your order ships or you'll be billed for subsequent shipments at whatever price Amazon charges then.