I kind of wondered that too. We use one box of 40 rolls of TP per month, which is now $18/month. Paper towel was a huge waste and we haven't bought it in years, but we used to use 1 roll/day at I am guessing $1 a roll? Thats $684 for TP and paper towel. I guess if you add in diapers & wipes that would really add up, but for just TP, paper towel and feminine products we are talking less than $700 a year for my family of 12.
I would still make the swap, but DH gave me a strange look the time I brought it up. lol