Florida has a long track record of all sorts of seedy behavior by physicians. They are still dealing with their pill farm scandals. With this particular doc, he was prescribing to patients a non-generic very expensive medication with medicare footing the bill. Its unclear why he was prescribing this particular medication as opposed to generic medications (which are generally cheaper). Its possible the drug was slightly better, I really am not sure. However, it appears that he was financially profiting from the use of these agents through the form of rebates from the drug company making this drug.
Kickbacks (direct payments for prescribing drugs) are generally illegal in this country. However, there are all sorts of ways a doc can profit from a drug company without direct payment (giving paid talks to other doctors for example). I'm not really sure how these rebates work, but it does sound very seedy indeed. Long story short, it sounds like he didn't do anything illegal, but I think that it could be considered unethical. If he simply sold the medication to patients as the best drug for them, without telling them that he was financially profiting from it, I think then he probably acted unethically.