Yea, i went into a phd program in biomedical sciences, spent 2 1/2 years doing computational biology, studying math, computer science and machine learning, not to mention working on project, then left. It was at the point where the prospect of out competing 7/8 of my fellow phd students was not work it, when all of my skills, where transferable to industry, even without staying for the phd. Part of me wishes I did stay, and I'll probably go back for a masters at some point. who knows. Anyway, the system really is designed to get phd students to do the heavy lifting, at 30k a year, for 6 year stretches. Why would I do that, when I have dropped out, and tripled my salary?