To my understanding, CPI does not weight amounts purchased, only general prices. I'm happy to be corrected if that's mistaken. Without the amounts, it's a linear combination of "we're being shafted" and "we can substitute those things left out of the CPI with some ease relative to other types of good." Income + substitution effects and such.

Your personal inflation is probably not 15% if you're not buying the exact same bundle of goods you purchased last year. Higher, yes, but if you substitute away or choose other options you're probably not expending exactly 15% more than last year.