Drug patents aren't guaranteed for life. Companies get a 20 year patent and then a generic form of that drug can be made. The generic form is identical to the branded version so not buying generic is a waste of money, and don't feel bad for the pharma corp that made the original drug, they typically have made billions in profits by the time the 20 year patent is over.

One issue is that pharma corps will often change the formula or delivery method of their drug just before the 20 year patent is up. This improved version of the drug gets its own 20 year patent. The original patent for insulin can be used by anyone...except its for extracting it from animals. The modern day insulin is human insulin and produced in a different way, but that patent is different so the company can keep it exclusive. Also instead of selling insulin in bottles companies have created automatic injection systems, which is great, but those also have patents.

While that sucks, most countries have universal healthcare and don't actually need to care about the costs of life saving drugs.