Generic drugs now make up around 80 percent of prescriptions filled, and many assume generics are always cheap. But a PBS NewsHour Weekend investigation found that's not always the case. Retail prices for generic drugs can vary wildly from pharmacy to pharmacy - a fact few consumers know anything about. The story was very personal for PBS NewsHour Weekend correspondent Megan Thompson, whose mother Carol discovered that the cost of a month's supply of her generic breast cancer drug Letrozole ranged from around $10 to more than $400 at pharmacies around the Twin Cities. Thompson also spoke to Lisa Gill at Consumer Reports who led a national survey of retail prices for five new generics. Gill said their results were unprecedented - the biggest price variations they'd ever seen in a drug pricing study. The consequences of these huge price variations can be dire. The uninsured, or people with inadequate drug coverage or high deductibles, could overpay by hundreds if not thousands of dollars. Or, they could end up going without medications they need. Thompson interviewed Lisa Duncan of Brooklyn Park, MN, who is bipolar and has a history of suicide attempts. After she became uninsured, she couldn't afford a big-name chain's price of more than $100 for one of her prescriptions, so she left the store empty-handed. Duncan says she found the same drug at CostCo for a tenth of the price and was able take the drug again as needed. As the nation grapples with skyrocketing health care costs, “Costly Generics” is an important consumer story that shines a light on the murky prescription drug marketplace, where it's hard to know how much drugs are supposed to cost, and is very difficult to find or compare prices. And vulnerable populations who need medications the most - the elderly, or chronically ill -- may also be the least likely to have to have the resources to navigate this opaque marketplace. One viewer wrote that after watching the story, she called around and found her prescription for $28 at a local drug store, compared to $72 at CVS.