[AnthonyMouse]

> Drug manufacturers regularly take approved medicines, which are off-patent and non-exclusive, due to safety reasons (side-effects, risks to patients) or due to commercial reasons: high cost of production, low demand, or possibly to increase demand for an exclusive alternative.

One of the big reasons is the cost of regulatory approval. Most drugs are cheap to make per-unit but if you're only going to sell to a few thousand patients, the fixed cost of regulatory approval means nobody does it at all, and then the patient has to buy a patented drug that costs a lot more.

Lower the cost of making generics and more people will do it.