The reason this Dr can prescribe such huge quantities and/or seemingly fatal combinations w/o multiple deaths from overdose to his acct is because he is prescribing for individuals with HUGE tolerances in all likelihood - people who have been addicted for considerable time and have very large habits.   

There are arguments on both sides as to whether he is performing a kindness or a horrific crime.  But he Doesn't seem to be *pushing* - getting the naive addicted.  And what he's charging, combined with the cost of the pharm, is a mercy compared to what people with this degree of a habit would have to turn up each month - likely from other people's property sold at an extreme discount. 
We Really need to rethink the Federal Laws and handling of addictive drug use and supply.  Priority: closing down the Black Market and profiteers