Three packages, three prices per bottle.
2 bottles: $79 each, $158, 60-day label, shipping extra. 3 bottles: $69 each, $207, 90-day label, free US shipping. 6 bottles: $49 each, $294, 180-day label, free US shipping.
The jump from $69 to $49 per bottle is the biggest step.
Moving from two bottles to three costs $49 more and removes the shipping charge. Going to six costs $87 more than three for three more bottles. Because the guarantee is 60 days for all, bigger packages put more money past the refund window.