My post is nothing unique to PT...it is generic to starting your own practice in any field (from law to an antique book shop).
I haven't read or heard any of the negativity you are mentioning...starting salaries for PTs in my area is ~70k. 5 years out, unless you left your brain in PT school, that's up to ~80k. Now, that is a 40hr work week. Add 10hrs of $50/hr per diem work, and you are grossing over 100k a year. Work up to clinic manager, and your base is ~90k plus a percentage of the clinics profits for the year, friends gross well over 120k in busier clinics, granted they work their butts off.
Now, if you put in the years, time, and effort it takes to start a business, then there is no ceiling.
This is no different for any other healthcare field...the numbers may be higher in medicine, but they pay their share of dues for the greater part of a decade before they are on their own, doing their thing.