Waterfall data (Value Change) in Matrix?

Let's see if this is what you need.

1) create slicers for the verions (A & B). Join A with an active relatioshionship to the fact table and B via inactive relationship

 2) Create the measure for the visual

Sum cost (A) = 
SUM(FTable[Cost])

Sum Cost (B) =
CALCULATE (
    SUM(FTable[Cost]),
    REMOVEFILTERS ( 'VersionA slicer'[VersionA] ),
    USERELATIONSHIP ( FTable[Version], 'VersionB Slicer'[VersonB] )
)

Difference = 
[Sum cost (A)] - [Sum Cost (B)]

% Difference = 
DIVIDE([Sum Cost (B)], [Sum cost (A)]) -1

And to make the slicers user friendly, create this measure to use as a filter in both slicers (set the value to 1)

Filter Slicers = 
COUNTROWS(EXCEPT('VersionA slicer','VersionB Slicer'))

I've attached the sample PBIX file