CAIRO — The housewives and breadwinners stepping out of a Cairo supermarket with bags of groceries agreed on one thing. “The prices are very high,” said Sabah Fehmi, 58. “The economy has been very bad after the revolution.” One after another, her fellow shoppers one afternoon this month in Nasr City complained about how food prices have risen since the 18-day winter uprising that toppled president Hosni Mubarak.