The increasing cost relates to drug companies running out of useful simple molecules. If you count the number of new drugs that treat common problems aka more than 100,000 people per year in the US and are not closely related to another drug you get a very tiny number of new drugs per year.

Sure we have a lot of drugs related to Morphine, but most of them are not significantly different from Morphine as to be worth high prices. When viagra goes generic at the end of the year the hurdle for the next male 'enhancement' drug ratchets up.