Hi Nasick,
Please go through what an virtual infoprovider does.
Virtual cubes are created for data reconciling.
It's not exactly an infocube. I'll give you a scenario. Consider you were reporting on some data.
Suddenly a new set of data from new source system arrives and you are not sure how the data quality in this system. But you'd like to check on that. In that case, you can go for virtual infoprovider and do reporting with the new data. If everything sounds fine, you can build a standard infocube with transformations.
I don't think it's cost effective in any way.
Remember, a virtual infocube doesn't stores data physically.
Br,
H