The 2-bottle package carries a shipping charge the 3- and 6-bottle packages don't — worth doing the actual math before assuming it's the cheapest way to test the formula.
The 2-bottle package is $79/bottle for a 2-month supply, totaling $158, plus shipping — while the 3-bottle and 6-bottle packages both include free shipping.
Since this formula's own materials describe memory-specific benefits as best judged over a couple of months, a 2-month supply on the smallest package covers only the earliest evaluation phase — worth weighing that timeline alongside the free-shipping value of the larger packages.