Pivot table shows irrelevant rows when added a Calculated Item

Hello Angjian and Welcome to Excel Forum.
This is an inelegant proposal that hopefully someone can improve upon.
1. Save the data in the Sales_Data table into a data model
2. Add the following measure: Difference:=CALCULATE(SUM([Quantity]),Sales_Data[Region]="West")/CALCULATE(SUM([Quantity]),Sales_Data[Region]="East")
3. Produce a pivot table from the data model
4. When the filters for both pivot tables are set to Cookies the other products are not show.
For aesthetics you could hide columns M:N
Sorry not to have been of more help.

Maybe like this (see the pivot table in the attached file).

I added two more measures
West:=CALCULATE(SUM([Quantity]),Sales_Data[Region]="West")
East:=CALCULATE(SUM([Quantity]),Sales_Data[Region]="East")
I still feel that there should be an easier way, however I also feel that this is the output you want.
Let us know if you have any questions.

Edit: Difference:=[West]/[East]

Glad I could help.

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You're Welcome and thank you for the feedback. I hope that you have a blessed day.