Calculate Pareto quickly

Rai_BI - Now that I know you need a static analysis, your best solutuion will be to create a calculated table that does all the calculations in one.

Below is the DAX to create this table, you can change the ABC variable to suit your classifications & remove any unecessary columns from SELECTCOLUMNS() to remove them from the table. 

To input this DAX go to Modeling > New Table.

VAR sales_by_prod =
    SUMMARIZE (
        fSales,
        dProducts[NAME_PRODUCT],
        "Prod Amount", [Sales Amount],
        "Total amount", CALCULATE ( [Sales Amount], ALLSELECTED ( dProducts[NAME_PRODUCT] ) )
    )
VAR cumulative_prod_amount =
    ADDCOLUMNS (
        sales_by_prod,
        "Cumulative Amount",
            VAR PrdAmt = [Prod Amount]
            VAR Cumulate_amt =
                FILTER ( sales_by_prod, [Prod Amount] >= PrdAmt )
            RETURN
                SUMX ( Cumulate_amt, [Prod Amount] )
    )
VAR _pareto =
    ADDCOLUMNS (
        cumulative_prod_amount,
        "paretopct", DIVIDE ( [Cumulative Amount], [Total amount] )
    )
VAR ABC =
    ADDCOLUMNS (
        _pareto,
        "Pareto Classification",
            SWITCH ( TRUE (), [paretopct] <= 0.8, "A", [paretopct] <= 0.95, "B", "C" )
    )
VAR Result =
    SELECTCOLUMNS (
        ABC,
        "Product Name", dProducts[NAME_PRODUCT],
        "Sales Amount", [Sales Amount],
        "Pareto Amount", [paretopct],
        "Pareto %", FORMAT ( [paretopct], "#0.00%" ),
        "Pareto Classification", [Pareto Classification]
    )
RETURN
    Result

This will give you a new table for analysis. 

If this works for you, please accept it as the solution.