Consulting Product
One thing most new consultants have a hard time with initially is the idea that our time (and intelligence) is our product. Our clients pay us by the hour (actually by the quarter-hour). This can be difficult for engineers who are used to designing a more tangible product.
This somewhat unique aspect of consulting (and attorneys) is very honoring...getting paid directly for brainpower.
Consulting in general has the age-old reputation: we are paid to tell you what you already know and do what you could already do. The things is: we continue to gain business because we can do it faster and better.