What to say to the best band in the world.

I'm speaking with a band and of course, they are selling themselves to me. The argument though is that they are really good. And by this time I haven't heard the music. But on and on they tell me that they have really great songs and are good live.

Some days pass and I manage to listen to the music, in fact, I get a hold of a live video from 6 months earlier. Let's just say this is far far away from the best band in the world. The live show is not even up to a local talent show.

Then they call again and after a couple of minutes they go for the same argument, we are the best band in the world.
The problem is that they really think they are. Maybe not the best but really good. You can easily figure out that they have some friends telling that to them, maybe also parents. How the hell do I break to them that the reason they are not progressing is since they are not good enough? In a sense it's like telling the guy in the subway that shouts out that Jesus loves me, sorry Jesus is fake Buddha is the real thing. It will just be an endless conversation about two different views.

I guess I will just move along and tell some advice to the band. Still knowing the error and that the advice is fruitless unless you are good enough. The sad part is that I know they will get back to me in six months telling me that they don't feel they have progression and don't understand why since they are the best band in the world.