Not 0, but vastly less than the cost of discovering and getting approval for a new drug. The vast majority of medical compounds are not particularly difficult to synthesize, meaning that the value of the process patent is relatively small. Once you release the drug, you will only have a very brief period before a competitor is able to come to market. In particular, they will not need to undergo clinical trials, which are very long (multiple years) and expensive (often hundreds of millions of dollars).