"I had ten more meetings with doctors all over the Bay Area—surely not all of them were ruthless capitalists like Susan."
10 meetings is inadequate. You should be willing to do 1000+ meetings if you really want this to fly (or prove it cannot).
You could also explore other business models (ie. rather than charging the practice directly find another way to make money).
Even if it fails, valuable experience, not a waste. Cool idea, and admire your initiative.