Answer:
B. Those who are unwilling to pay actually do not want to listen to the music.
Explanation:
If true, the remark (B) suggests that Joan's final calculation may not appropriately reflect the quality of the street musicians playing music.
It's because when Joan reviews all of the reactions from that point forward, the final estimate indicates that even individuals who don't want to listen to the music really appreciate the music and so want to listen to it.
That is not true, though, and therefore Joan's latest assessment may exaggerate the music's significance.
So the correct response is (B).