Design is the sum total of decisions which make a product serviceable and attractive. In this sense, questions about whether design is necessary or affordable are quite beside the point, design is inevitable.
Good design is simply the result of making decisions consciously, at the right time, and in consultation with professionals as the need arises.
Graphic Design should not be something that is added on the outside of a project, like the icing on a cake. It is the process of identifying communication needs and then resolving specific problems with visual solutions.