No holder of any wholesaler’s permit shall ship, transport or deliver within this state or any territory therein or sell or offer for sale, to a purchaser holding a permit for the sale of alcoholic liquor for on or off premises consumption, any brand of alcoholic liquor, including cordials, as defined in section 30-1, at a bottle, can or case price higher than the lowest price at which such item is then being sold or offered for sale or shipped, transported or delivered by such wholesaler to any other such purchaser to which the wholesaler sells, offers for sale, ships, transports or delivers that brand of alcoholic liquor within this state.