The smallest package tier here carries a shipping charge that the larger packages don't — worth factoring into your actual total cost comparison, not just the per-bottle price.
The 2-bottle package adds a shipping charge on top of the $79/bottle price, while the 3-bottle and 6-bottle packages both include free US shipping plus the six bonus guides.
A seemingly small shipping fee, combined with missing out on the bonus guides, changes the true total value of the smallest package — worth adding both into your comparison.