You raise a good point and percentage increases can be deceiving. If a drug cost $0.01/tablet and now it's $0.03/tablet, yes that's a 300% increase, but it still costs pennies per day to treat someone.

Unfortunately I can't find it right now, but the Us gov't did a study into generic drug price increases. There is no one reason why they went up. For some drugs it was because a company decided to stop making it and there were shortages. For other companies, they had manufacturing problems and shortages resulted.