When you increase the supply of anything, its value relative to everything else goes down.
You are conflating price inflation with inflation of the monetary supply. The former usually follows the latter, but not always. Many (most) people make the same mistake.
In your example the purchasing power of both the individuals income and savings has decreased 50% relative to the example ‘item’.
A better example is to imagine that the guy was paid two ‘items’ a month and had one ‘item’ in the bank.
Fast-forward and he’s being paid one item a month and his item in the bank had to be cut in half. This is why inflation is called the ‘cruelest’ tax; as its really a tax on wage earners, savers and those with a fixed income.
For fun try plotting your salary over the last decade in barrels of oil instead of dollars.
