Inflation is something that occurrd in even ancient class societies. It is noted in ancient societies that they originally issued silver coins for daily use, but as the centuries passed by successive governments debased the currency until copper coins were being used, then iron, then zinc and now today most money is digital, being produced at close to 0 cost.

The reason why Inflation happens in class societies is that the state debasing its currency, or banks increasing their lending (both of which cause inflation by jncreasing the money supply) are easy ways for the ruling class to generate financial power and keep liquidity in the economy up.

Another aspect to this is selection pressures for businesses. “Inflation” and “deflation” are statistical properties of an economy. That means that they exist as the sum of many small interacting parts (the prices of individual commodities).

If any business lowers their prices pre-maturely while everyone else keeps up their prices, the business will loose profit and thus shrink relative to others. This is a strong disincentive against deflating prices except in dire circumstances (recessions) where you can safely expect everyone else to also lower prices.