I just want to get this clear.
The performance penalty in games due to ray tracing is not because CU’s are busy doing ray tracing stuff like BVH traversal or something. The performance penalty is there because of the Ray tracing, the scene is more accurately detailed compared to traditional render pipeline. To shade more detailed scene, more power is required. And if power is limited, we see performance dips.
This is my understanding as for why RT has performance penalty in games. I have made this opinion on the basis what DF has said about RT performance.
Feel free to add more to this. Or maybe explain otherwise if i am not accurate enough.