Hello Albert,
COSTPERUNIT is a stored Key Figure at its base planning level, but if you check the request level you will see that is defined using the following calculation DEPENDENDDEMANDCOST / DEPENDENTDEMAND. This calculation which is on top of the storage will provide a weighted average.
Imagine that you have:
Prod A, Loc1
COSTPERUNIT: 2
DEPENDENTDEMAND: 10
Prod A, Loc2
COSTPERUNIT: 5
DEPENDENTDEMAND: 5
If COSTPERUNIT at request would be a simply average, you would have (2+5)/2 = 3.5
But using the calculation, the cost on aggregated level will result into: (20 + 25) / (10 + 5) = 3
This is the reason why in the calculation graph you see all related KFs.
Hope this helps,
Alecsandra