Hi Srikanth,
we see this quite a lot. It all comes down to how you wish to have the various reports represented, and so there are many approaches.
One approach that we have implemented in a number of customers is to allocate Vendor Project costs from Vendors to the Projects model, and ensure these costs do not allocate from Vendors to ITRT.
By doing this the Project and Vendor reports will both show the complete story, and you will most likely get a more accurate of App TCO.
Hop this helps
Michael