Also, brand name and generics are tested to the same tolerances. If the generic is allowed 10% margin the brand is too. In fact, sometimes they're made on the same production line. A few years back when generic Protonix came out it was a huge issue, as it was extremely easy to mix up the "brand" and "generic" because they looked identical and came in similar packaging. I remember hearing about pharmacies getting fined for supposedly mixing them up. If there is any chance of a mixup between brand and generic (missing DAW is a common typo) you had to throw them away because there was no way to tell them apart.
Something else you overlooked, related to the above, is that "Brand name" companies typically own as least one subsidiary that produces generics. For example, GreenStone is 100% owned by Pfizer, so i have doubts their generic products could be any different.
I'm not normally a dick on HN but I don't appreciate people blowing facts out their ass when it relates to common misconceptions. The drug companies want you to believe generics are inferior, and they spend more on marketing than drug research. You should speak to some pharmacists if you want honest opinion on the matter. They're easy enough to talk to and I think you'll find that the vast majority share my opinion.