I don't care about the egotistical part, but the point about rare diseases is dead wrong - those are exactly the diseases, if suffered by the right (read: wealthy, Western part of the world) that are enormously lucrative to pharma. The diseases that are not lucrative to pharma are things like malaria.
The things most lucrative to pharma are problems whose number of affected patients (x axis) and price to treat (y axis) create a box with the highest volume on a graph. That is, things which are expensive to treat, yet treatable, which many people have (common, not rare). Things like diabetes, cancer, etc. I don't think Hashimoto's thyroiditis would fall into that category.
But, both of your driving factors, affected patients, and price to treat, are in turn driven by other factors such as competition, targeting symptoms, and the cost of research.
While perhaps not blockbuster, orphan drugs for rare diseases can turn quite a profit for pharmaceuticals.
