Drug prices

Pharmaceutical companies spend huge amounts of money to develop new drugs. Then, if the drugs are effective, many people can't afford the treatment because the price of the drug is too high. The drug companies' justification for the high price is that they need to recover the cost of research and development while the drug is still under patent. My suggestion is that governments should buy the patents of certain drugs, so as to to reward the companies that developed them, and at the same time make them available to people worldwide at an affordable, generically-produced price. This could be done unilaterally by individual countries, by small groups, or by the United Nations. Why is this type of foreign aid not even talked about?