A lot of cost of drugs comes from R&D, quality control etc. The chemical synthesis itself generally isn't that expensive. And expired pills would be a quite unp

A lot of cost of drugs comes from R&D, quality control etc. The chemical synthesis itself generally isn't that expensive. And expired pills would be a quite unpredictable precursor, which isn't very desirable in the pharma industry (or anywhere else for that matter). In other words, I doubt you could make much of a profit (if any) from purifying non-decomposed chemicals from pills.