Prices of articles can vary due to changes in the price level and due to other causes (such as obsolescence, changes in consumer preferences, and so on). CPI o

Prices of articles can vary due to changes in the price level and due to other causes (such as obsolescence, changes in consumer preferences, and so on). CPI only informs us about changes in the price level, it doesn't tell us anything about anything else. So the fact that the price of a particular article hasn't changed exactly according to CPI is completely normal, and not a reason to believe that the CPI is "wrong".