Cost Roll up where Component Item Cost is 0

Summary: We have both B2B buy and Make Flow. For B2B make flow, we create star item (configured item) which contain another star item (sub-configured item) inside this. During cost roll up we process the roll up with Scope "Unprocessed purchase order and work order". When cost roll up of subconfig item comes out as 0, the cost roll up of the star item getting failed, is it expected?

As per below screenshot:

Scenario 1:
star item (configured item) A*B consist of A, B, and another subconfig item X*Y (which consist of only X).
In case of cost of item X set as 0, the roll up of subconfig item is getting failed and hence config item's cost as well is not getting established.