To the economists out there: how much is inflation a self-fulfilling prophecy? Are people who set prices known to think: "hey, we're in an inflationary market, let's jump our prices too!"?
Lack of competitors able and willing to sell at lower prices is also necessary, i.e. low supply.
Everyone wants a 9% raise, everyone wants more for their products because operations cost more, inflation rises even more next month, rinse repeat
People is the important word in the question.