In my household, there are a few items that we go through regularly; toilet roll, toothpaste, and kitchen roll.

Most people will buy these items when you need them.

Personally, I like to buy them in bulk from wholesale.

Cost Breakdown

Bulk Toilet Roll Cheaper Supermarket Toilet Roll
Quantity 108 9
Total Cost £26.29 £2.00
Cost Per Roll £0.24 £0.22
Adjusted Cost Per Roll
Accounting for 320 sheets
£0.16 £0.22
Cost for 9 rolls £2.18 £2.00
Adjusted Cost for 9 rolls £1.44 £2.00

Conclusion

Once you take into account that toilet rolls I bought in bulk had 60% more sheets than the cheaper supermarket equivalent, then I was making a 28% saving in the long run.