It all depends on the company producing the generics. Many recent PPI's are still on patent, which means that there is no alternative than the brand name. Others such as Protonix, for example, are available as a Generic. I like Teva Pharmaceuticals, since they produce many great Generics. However, some from India are not of the highest quality and you might wish to check different major pharmacies as to where they source them. Some new PPI's have discount cards which really help in making them more affordable.
Usually it's the insurance company that makes the decision on how much you pay, but I don't know anything about
your insurance and/or financial situation.
One other factor to consider, is whether the PPI is not doing it's job, or the relfux is getting worse. On that subject you should defer to your MD before purchasing more PPI's in the case that it might be changed.
Hope this helps.