In reply to NiLu:
With overhead, I meant all of it. But it all has to be looked at relative to the cost of the the class you want to build, and the relative number of object you need to work with.
Every object derived from uvm_object has a string name and int id variable. An then there is the extra constructor call.
BTW, copy() is non-virtual, but most often you will want to use clone(), which is virtual.