For example, if filtering A category, the charts should display three lines.
One for subcategory A1 monthly price trend, one for subcategory A2 monthly price trend
the third line should show aggregation . The logic for aggregation is sumproduct(price,sales)/total sales for subcategory A1 and A2.
Is it clear?
I don't know if I've understood, but if I have, maybe remove Category from that table, and add a new table:
Category, Sub Category with Category Total, Sub Category
A, A total, A1
A, A total, A2
A, A1, A1
A, A2, A2
And do your chart like this:
Dimension = Month
Dimension = Sub Category with Category Total
Expression = sum(Price * Sales) / sum(Sales)