There is no way to quote a price since nobody saw what is inside the brake drum. You may need nothing but the four grease seals or you may need entire brake assemblies plus drums and wheel bearings. Anyone who quotes a price without seeing inside each assembly is a crook by definition. This is such a simple job that any mechanic or do it your self type can do it. One problem with taking it somewhere is that the lowest skilled (read lowest wage) employee will be assigned the job. One more thing, lose the grease gun.