Optimize SUMX / SUMMARIZE Measure

Hello, I'm not sure if you have figured out why it was slow, but I think it's probably 
your if statement in your SUMX.

SummedPriceImpact =
SUMX (
    SUMMARIZE (
        'Fact',
        'Customer'[Sales Team],
        'Customer'[Sales Man],
        'Customer'[Customer],
        'Store'[Store],
        'Article'[Article]
    ),
    [PriceImpact]
)

I see 2 things :
1) [PriceImpact] triggers Context transition for each iteration which is bad with a Big Fact table
2) You should always avoid using IF statement inside an Iterator like SUMX. The use of IF statement will require a call to the Formula Engine for each iteration and the iteration is done by the Vertipaq engine.

One solution to speed up the process would be to precalculated your [PriceImpac] measure inside a Calculated column in your Article Dimension. It will be stored in memory.

Maybe I did not understand your problem very well and this won't work for you.

Also 2M rows is nothing for a Tabular model. You should be able to have a speed < 1sec like the other person said earlier.