Sales and Cost Pareto(Customer) = 
//Find Current sales
VAR _Selectedmetric = SELECTEDVALUE(Inputs[Dim])
VAR CurrentSales = IF(_Selectedmetric="Total Sales",[Total Sales],[Total Costs])

//Find Overall Sales
VAR AllSales =
    CALCULATE ( IF(_Selectedmetric="Total Sales",[Total Sales],[Total Costs]), ALLSELECTED ( Sales ) )

//Find sales by customers
VAR Customersales =
    SUMMARIZE (
        ALLSELECTED ( Sales ),
        Customers[Customer Names],
        "custSales", IF(_Selectedmetric="Total Sales",[Total Sales],[Total Costs])
    )

// Find current Cummulative Sales
VAR cummsales =
    SUMX ( FILTER ( Customersales, [custSales] >= CurrentSales ), [custSales] )

//Return percentage contribution
RETURN
    cummsales / AllSales