How much does advertising and marketing add to the price of products in grocery stores? Can Amazon reduce that extra cost by reaching people in new ways, or by

How much does advertising and marketing add to the price of products in grocery stores? Can Amazon reduce that extra cost by reaching people in new ways, or by creating its own brands? Store brands are generally pretty good and cost less. Maybe it's food manufacturers that should be worried, not retailers. The premium one pays for advertised brands might become a thing of the past.