I hear this all the time. "I went to doctor X, who's famous, and my botox didn't take. I must be a rejector or super user of Botox." Okay, this doesn't happen. What is happening is that these "doctors" are either diluting Botox so much that it's not effective (so that they can make more money on a vial) or they're just not injecting enough. When you went back he realized the issue and injected maybe the correct amount.
Most Plastic Surgeons don't make any significant money on Botox because we look at it as an adjunct that is needed. We make our livings off of surgery. Other physicians, primary care docs, gynacologists, orthopedists etc., use Botox to make money. So they dilute the vial and inject limited amounts making the vial last longer and make more money.
See a Board Certified Plastic Surgeon and understand how many units of Botox you will recieve.