[matthewdgreen]

It’s a huge amount. I have a seizure disorder and I have to carefully increase my dosage by as much as 50% to compensate for the difference between generics and brand-name. The 20% is an average: one of the big differences between the two is absorption before/after you’ve eaten, so taking the medicine on an even slightly full stomach dramatically reduces absorption. The brand-name manufacturer now charges $300/mo for an off-patent drug you can buy generic for less than $25 (without insurance) which illustrates their view of the perceived value.