[bradleyjg]

My great-uncle went pure math (he had an Erdős number of 1), a brief sojourn in industry, pure math.

From the stories I've heard the industry stint was purely about money. He had grown up very poor and had four children, a few years working on oil field and bond models was enough to supplement his professor salary for the rest of his career.

On the other extreme is someone like Simons who left pure math to found a hedge fund and is still at it billions of dollars later.