Toilet paper math is the hardest kind of math. According to the print on various different packages of Charmin, and I could not make this up:

12 Mega Plus rolls = 54 Regular rolls

30 Double Plus rolls = 68 Regular rolls

12 Super Mega rolls = 72 Regular rolls

18 Mega rolls = 72 Regular rolls usually, but sometimes are sold as "Bonus Mega = 82 Regular rolls"

They can keep the sheets per roll the same and still give us less for the same price if they reduce the dimensions or thickness of the sheet too. They should just give us a weight assuming the paper is less expensive than the cardboard roll inside.