We recently tried a cost savings experiment by switching toilet paper brands – from 2-ply Charmin Ultra Soft to 1-ply Scott, which was the cheapest by unit price. However, we have since discovered that we probably end up using twice as much toilet paper as before, since Scott is not as thick or absorbent as the Charmin. I think it is worthwhile to experiment with other brands to maximize the value we get, but this is one situation where knowing the unit price was not the whole story.
On a related note, this Luxe bidet attachment has been the best way for us to save on toilet paper.
On an interesting different note, when I was researching toilet paper, I learned that mega-stores like Walmart might have generally cheaper prices on items like toilet paper, but when grocery stores like Kroger or Safeway have their sales, they can beat those prices. Grocery stores hold their sales about twice a month, at the beginning and middle of the month, to coincide with pay cycles. A mega-store might have the same kind of sale (at approximately the same prices) only four times a year.