The artist has no sort of guarantee of income from any particular piece of work or really even subsistence from their entire life's output of work.
I think most people would agree that the physical trades and the arts are not well-suited for comparisons. They are just fundamentally too different.
How is the writing of a book, the production of a movie or the recording of a song any different from the building of a bridge, the drafting of a contract, or the provision of management consultancy? How are they "fundamentally too different" if it's not the way we pay for them?
But more importantly, how is is that we see this difference as so fundamental that we afford protection to an artist (or more accurately, their publishers and the industry that surrounds them) via copyright for so long?
You do not get to clone the shovel by magic for about .1 cent and sell 50M copies of it for $20 each for the next forever.
Again - the copyright system as it currently exists needs to die. 7 years protection is enuogh.
The point was not to defend the current copyright system and certainly not some of the more notable abusers. You asked a question, and that that is one part of the answer. Writing a book or doing any form of creative information-product work is different from doing physical-product or service work.
If you want to make money, open-sourcing your work seems to be a very hard way of doing so.