Some hard examples: When Alan Moore was denied the right to use the Charlton characters for Watchmen, he came up with new characters. When the Dr. Who episode “Shada” was shelved, Douglas Adams rewrote the story as a Dirk Gently story. In both cases, the artists were restricted from using characters someone else had come up with and had to rewrite their stories using original settings and characters. In both cases, the resulting works were better than they would have been, they expanded the repository of human expression more than they otherwise would have, and the result was better for culture, better for art, better for humanity.
When Rowling was creating the Harry Potter stories, she was living in part on government assistance (so I understand). She had an idea and saw the opportunity to create and improve her financial condition. It was a wild success, creating a new franchise, a new industry, enriching scores of people in the entertainment and publishing industries, as well as herself, and bringing a high grade of entertainment and inspiration to millions of people.
In the absence of copyright law, she would have had to spend her time working on a different career path. Likely, Harry Potter would never have been written because she would have perceived less potential benefit. If she had worked on it anyway, while holding down another job, she would have had less time to develop, affecting its quality. And even then, she would have faced negligible benefit, because large industry players (likely the technology industry, in the absence of a large entertainment industry) would have snapped up all the potential profit.
The broad and diverse range influences exist as they do today because of copyright protections. In their absence, there would have been (1) fewer musicians (2) with less time to develop their art (3) leading to many many fewer and more expensive recorded works and (4) fewer and more expensive live performances.
If $20 is too dear, then the alternative would have stifled the young musician’s access to influences even more. As others have made the point, mass entertainment, mass culture, mass art depends on the copyright system. It allows a creator the freedom to dedicate time and energy to creation and to spread its cost over many consumers.