The effect on the price index is likely overstated ; this is called the substitution effect.
Explanation:
For a given type of goods or services in the given area, a price index is a weighted average of price relative to that class over a given period of time.
It is a metric to allow you to measure the gap between the time periods or geographical locations of these price relations as a whole.
From an investor point of view, the CPI, as an inflation proxy, is a critical measure which can be taken to nominally estimate the total return that an investor needs in order to achieve its financial objectives.