2

On the right add new Repeating Group “A” - same datasource as your left repeating group but add :each item's Client:unique elements

Inside the cell of RG A add a Repeating Group “B” with the same datasource as your left repeating group but with an additional constraint Client = Current cell's Client

Also inside the cell of RG A below RG B is your row to say “Current cell's Client's Name’s Total” and another text element with the same datasource as RG B but add :each item's price:sum