There is a lot of muddied water when you start looking into the economies of toilet paper. Some would like you to believe that their paper system gives the best "Cost in use" because of something or other.
The fact is, all things considered, give or take, it is metre for metre of paper than counts, as long as the thickness is the same. In other words you can't compare a 3 ply with a 2 ply paper.
However most commercial toilet paper systems are 2ply and a very similar thickness.
So, cut the crud, what is the cheapest way of buying toilet paper?