RAII has nothing to do with reference counting, it stands for resource acquisition is initialization. In C++ that means the lifetime of a resource is tied to the creation and destruction of an object. Often when people talk about RAII and C++ they are also referring to destructors being called when an object goes out of scope, so if an object that contains an object containing some allocated resource goes out of scope, the resource is released as the destructor path is called.

If an object with a smart pointer goes out of scope, then of course there's the overhead of the smart pointer, but the previous comment wasn't referring to that situation