Answer : It depends on the designer's level of experience, the size and scope of the project, and the region of the country. Generally speaking, kitchen designers make anywhere from $50 to $200 per hour. Some may charge a flat fee for a project, while others may charge by the hour.
Keep in mind that most kitchen designers offer a wide range of services, from initial design consultation all the way through to final installation. As such, it's difficult to give an accurate estimate without knowing more about the specific project at hand.