Think in pools. Prices are just exchange rates between pools (equilibrium). And mostly units in the pools are not destroyed. In the nonstatic fiat pool more units are added (inflation), so exchange rate from fiat to other pools is going up. You can define inflation as the amount of units increasing. You can also look at it from the exchange rate point of view. If goods and services increase faster than the inflation of fiat, one would experience decreasing prices.

It's all relative. And all based on supply/demand mechanics.