Making calculations based on data appearing on Pivot Table (not its source data)

Hello!

I have attached a sample sheet.

In this sheet, you will notice:
- John has purchased breakfast 2 times
- Sarah has purchased lunch 2 times
- Steve has purchased dinner 2 times

I want my pivot table to have an additional column showcasing the "Average cost of each transaction". Is there some function that would allow me to show what the average cost of each individual's meals are? Can this be done without modifying the source table?

I have to perform such a calculation for thousands of cells but everytime I try and add a calculated field with "Total/ID" it returns the calculation using the "ID" from the source data and not the "Count of ID" we see in the pivot table. So for Steve's dinner, it wont calculate "$65/2" it will calculate "$65/A132"

Any help would be very much appreciated!!! This has been bothering me all morning