The easiest way to put this is: there are many brands of potato chips, all priced differently for what is the same product - potato chips. Not all brands follow the lowest price in the market because there are inherent strengths to a certain brand and their product for which they believe they can charge more. At the end of the day, as long as there is demand for a more expensively-priced brand of potato chips, the prices of that brand will rarely reach that of the lowest in the market.