I can tell you from personal experience that the overhead not including employees will run about $10,000 a month if you watch your pennies and lease used equipment. If you want a nice space, new equipment and good software, the overhead would be close to that $200,000/yr figure. If you worked 60 hrs per week, you could make a little money.
For a standard clinic with staff, billing support, transcription overhead is over $500,000. If you are employed with a profit sharing plan, the usual figure for breakeven is given at about $1,000.000 per year.
He doesn't have any of that overhead. He is just one person in an office. No receptionist, etc.