The production cost of a tablet is typically less than 5 cents and this includes the packaging.The tablet is made from talc, sucrose a few chemicals mixed together. Now I know there are R&D costs, clinical trials and FDA approval for the original patent but once a pharma company receives a patent they're covered from any competition for 10 years unless they decide to licence the patent.
And in the pharma sector, profits can very quickly turn to dust when something goes wrong with a drug. Look at the ups and downs of Elan as an example.