If there’s an actual generic (e.g. Naproxen Sodium :: Alleve), then your doctor just has to ensure that the Rx isn’t “fill as written”. The pharmacist can then offer you options (Namebrand at X times 5 or generic at X)

If it’s the case where there’s an older generic and a newer product still under patent, that’s a discussion with your doctor: Is the newer product worth the money, or should I stick with the older thing?