The publication describes two ways of shopping, taking into account the CPI (Consumer Price Index) inflation rate. In the first case, changes in the sales price are made in a continuous manner in accordance with the inflation rate, and therefore it is better to make larger purchases. In the second case, it is better to carry out smaller purchases, because it is characterized by one-time adjustment of sales prices to the entire purchased a lot of goods. Both cases were verified based on the Solver tool, using non-linear, integer-based optimization. The final result was to determine the optimal purchase quantities with the minimum inventory costs.