Product is indeed very important and valuable. It is the product that mostly catches the attention of the possible investors. Mostly projects with products proves there worth and legitimacy.
Precisely, project can only be called a successful with a good working product. And definitely important to gain a reliable profits.
Well that mainly determines of a project is profitable and legitimate or not. I'd have doubts in investing on projects that wouldn't have working products or at least have that in their road maps. It's hard to just simply invest because you heard something good in an ad so research is essential.