The practice of pricing different strengths identically is very common
with brand name drugs.  The idea (well, if you could call it that) is to
remove any incentive to underdose patients out of concern for cost.  It
may be possible to split a tablet (not the capsules) if the strength is
a clear multiple of your dose.  But if you're in the (fortunate)
position to take a drug for Alzheimer's, the primary goal ought to be
taking the full therapeutic dose.