When I buy toilet rolls at the supermarket, I look for rolls with the ply count I want, take the price and divide by the number of sheets to determine the best value one to buy.
You cannot use rolls to price it because some have 200 sheets per roll and some have 220 sheets per roll.
Of course the final criteria is whether you like the paper fibre quality and the embossed design on the rolls. I am partial to sea shells.
I find house brands tend to have the roughest feel and I won't buy those even if they are the cheapest.
Buying toilet rolls is both an art and a science. Your wallet and backside will thank you for your efforts.