well R&D often proves very costly.Look at Raptor,Lightening,Lavi,Typhoon and LCA these all associated huge costs multi billion dollars and time.Why we need J-11? we should more inficize on technology rather then planes. Also R&D should done & should part of the plane which is completely missing in PAF. China, US are going for space war and we are still sitting in airodynamics era.
PS: I am nothing talking about studying the buying models but actual R&D.
if we have of the shelve tech available with ToT then it is better.We can improve on it with time somthing new is not suitable for PAF like resource constrained AF