- Explicitly say that it is a hypothetical example
- Create a highly realistic artificial customer (1 owner, 3 trucks, 1 warehouse, $x million in annual revenues, etc.)
- And most importantly: explain how you get to your cost savings. If possible break them down into a few simple categories, and use a highly simple and transparent way to quantify them (10 instead of 35 phone calls of 30 minutes each per week equals $x)
- Make the spreadsheet as complicated as you want, but start with a blank PowerPoint/Keynote page to explain your calculation.
- Add everything up and see whether the cost reductions make sense as a % of the total
The main purpose of the case example is to explain how you got to the savings, not the absolute point estimate.