Why get an expensive tuner?Am I missing something?

Maybe I'm missing something and need to be educated so please correct me if I'm wrong, or agree if I'm right. But how much sense does it make to spend a lot of $$$ on a tuner when the source is of lower to questionable quality? Isn't that sorta like having a cheap cd player (i.e. the source and the mode of transmission) and then everything downstream being of better quality? The sound can only sound as good as the source and for some reason I don't think radio stations shell out a lot of money to broadcast a high-end signal.
What do you think?
Happy Listening!