A full and complete answer is beyond ELI5 but a big part of it is perception.
People don’t really notice a single year change. When you look at the prices in the store and think about what the price used to be it’s probably the price from several years ago.
So a report comes out and says inflation was 3% and was 10% last year and 6% the year before. The total inflation was 20%, which would make a $5.99 item now $7.19. And now the second issue, your brain just saw the price go from $5 to $7, which would be 40% increase instead of the actual 20%
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