Burger King will offer a new $1 French Fry Burger starting Sept. 1. The new item sandwiches four fries into a burger with a standard beef patty, a company spokesperson said in an email. The dollar still rules on quick-service menus, noted Leslie Kerr, president and founder of Intellaprice, a Boston-based restaurant-pricing advisory firm. “The dollar remains the most common price point on the menu by far,” she said.