Many housewives complain that prices are too high.
Literal
Prices [subject-が] high [quotative-と] complaints say housewives [subject-が] many.
物価が高いと不平を言う主婦 is a relative clause modifying 主婦 — 'housewives who complain that prices are high.' 不平を言う means 'to complain.' The が after 主婦 marks the subject of 多い (are many).