I feel it's necessary to correct what I said because it's not
completely correct.
I said that "sharing knowledge" was the main reason for models. That's
not true. There are a lot of reasons people make models...as many
reasons probably as there are people.
In the field of science and engineering, models are often published to
add to public knowledge and there is usually some form of compensation.
In science, one has the right to claim the first (and an obligation to
reference ones source), in engineering, there are several reasons,
including compensation.
My usage in my last post only referenced the smaller realm of science
and public engineering.
Engineering models are often paid-for products. In fact, in the
specific realm of this discussion, there are models that can be
purchased to address exactly the issue of estimation of project scope.
