Of the top 10 Generic Viagra prescription drugs sold in 2007. the top prescription sold in 2007 was the generic version of Cialis and Viagra. Generic Viagra The American public spent over $286 billion on prescription drugs in 2007. With the price of generic drugs averaging 30 to 80 percent less than the cost of brand-name drugs, the American public can save billions of dollars by using generic drugs. Overall, these savings can help control the cost of health care in the U.S. without reducing the quality offered to patients.