Advantages of powerpivot over pivottable from DAX book

[stephme55]

I'm reading this book and the author says" Stop and think about that 'rearrange the pivot and the formulas still work' point for a moment". Let's say your workgroup originally requested a report that displayed Sales per Day and Sales per Transaction grouped by Month. How would you build that report in normal Excel? You couldn't just write formulas in a pivot. You've have to do some pretty serioues formula alchemy to get it working"

Wouldn't it actually be easy to do that in a pivot table? I don't see the different between creating the formulas in a pivot table vs. creating them in powerpivot. You would just create a calculated field in pivot table for Sales per Day and Sales per Transaction in the pivotable. The transaction doesn't exist, but you could just create it in the pivot table with a count. What am I missing?

[romperstomper]

A little context would be nice but calculated fields in regular pivot tables always sum the source fields. You can't do a sum of one divided by a count of another for example. DAX is much more flexible.