The sheepskin is utterly irrelevant for selling consulting engagements. If you develop a particular skillset which happens to be commercially useful in graduate school, such as machine learning or whatnot, that can potentially be helpful. It is neither necessary nor sufficient to study a subject in graduate school to make that subject commercially useful.

With regards to selling software, the only time in eight years that I've had anything about my college education matter was when an insurance company asked me whether I was formally trained in systems engineering, since they believed it decreased their risk for writing professional liability policies. My answer was bachelor's in CS at a good university, but they told me they also would have accepted "Have done this for five years" (which I have).