It seems to me that the question of artistic merit (as subjective as the broader question of taste) is being subordinated to the test of whether the "artist" has been paid or not.

Is that really a valid criterion, especially when we don't know (except in rare cases) who was paid for what and who wasn't or under what circumstances?

Most great artists have been paid for their work, even if inadequately, and even if payment was not on their minds while they were working.

And, of course, it almost always was, whether they were trying to please a patron or an audience, or simply expressing themselves.

Is it true that a pop song or an "art song" that has been written for money is necessarily an inferior work of art, or necessarily insincere? If so, on what basis?