Nor is the artist in this scenario!
They are merely saying that they have made a limited series of objects they wish to assign a price to, if the market will pay.
But if the people who can buy it can sell essentially identical reproductions for whatever price they choose, then its assigned product price tends to zero too.
If you follow your own argument, then what you are saying is that compensation for effort can only come from a one-time contract. But since intellectual work is not then protected by copyright, those contracts are really difficult to write, because the buyer is not getting any unique thing either.
It doesn't take much to get from "there's no such thing as copyright" to demand collapse for almost every industrial product. Would we even have the PC if there was no copyright protection for intellectual work?