Sum and count customers in different value intervals

If you create a parameter table with the ranges you want like this:

then with Range Table desciption on rows, use these measures: 

Number of Customers =
COUNTROWS (
    FILTER (
        ADDCOLUMNS (
            VALUES ( CustomerID[ID] ),
            "Total Sales", CALCULATE ( SUM ( Sales[Sales] ) )
        ),
        [Total Sales] >= MIN ( RangeTable[Min] )
            && [Total Sales] < MAX ( RangeTable[Max] )
    )
)

Total Sales for Group =
CALCULATE (
    SUM ( Sales[Sales] ),
    FILTER (
        ADDCOLUMNS (
            VALUES ( CustomerID[ID] ),
            "Total Sales", CALCULATE ( SUM ( Sales[Sales] ) )
        ),
        [Total Sales] >= MIN ( RangeTable[Min] )
            && [Total Sales] < MAX ( RangeTable[Max] )
    )
)

 I freehanded these and didn't test them, but they should be close.