Comment by triplepoint217

Writing the 100 page thesis is not the hard work part of a PhD. Doing the research to have the results to write that thesis is the hard work. Unless you are uncommonly lucky, you will fail at some avenues of research and have to slog through lots of painstaking work. I don't (yet) know how that compares to the challenges of a startup, but a PhD is an entirely different animal than an undergrad degree (for better or worse)