Markups on cereal, especially name-brand cereal, tend to be pretty high. So warehouse club savings of close to 50 percent for bulk sizes can be hard to pass up [source: Wallet Pop]. And most of the warehouse clubs carry double-sized boxes of brand-name cereals. Supermarkets also offer regular sales on certain brands, so that can be a good time to stock up. But like anything else, be sure that you're not sinking money into a brand or flavor that you'll be tired of quickly, or buying so much that the same kind gets tiresome. That can be especially important if you have children whose tastes might change from week to week.