https://www.fda.gov/drugs/abbreviated-new-drug-application-a...
The US has some of the lowest cost generics in developed nations - prices tend to be lower than the EU. The US has some of the highest generic drug penetration of developed nations. [1] That's because of things like the 180 generic drug exclusivity and mandatory generic substitution laws.
The 180 exclusivity is a big part of that. If you open the flood gates to any generic manufacturer, the margins disappear so quickly that some manufacturers won't even bother to try. By dangling a massive carrot whereby the generic manufacturers can quickly recoup costs and make a large profit, it drives generic companies to compete to the enter the market.
When Lipitor went off patent, eleven generic companies entered the market and prices dropped 95%.
The US generic market is one of the best functioning in the world.
An epilepsy medication I took, once the patents completely expired (both on the regular and extended release versions), the generics ended up costing me more to pick up while the branded version rose in price as well.