Cumulative total by category -Measure

Does this work for your context?

Sum by Product: = 
CALCULATE(
    SUM('Table'[amount]),
    ALLEXCEPT('Table', 'Table'[product])
)

//Removes filter context from the table except for product

Result:

https://docs.microsoft.com/en-us/dax/allexcept-function-dax

If this works for you then please select as Answer.  All likes and Kudos appreciated.