Or any UGL, when India pharma is so cheap.
Look into tablet manufacturing some time. It requires careful selection of excipients because different active ingredients "clump" with certain excipients (they call it the "hazelnut effect" when you get a random ball of concentrated active ingredient in a random tablet), and then each ingredient has to be ground to a specific particle size for that specific formula, and after all that, a 15% variation from table to tablet is considered acceptable.
Just dumping the active ingredient with some random excipients and mixing may give you 98% of the pills being close enough to the advertised potency, but there will likely be a few duds, and some extra "hot" tabs in there. A real problem depending on what the drug it is.