Price is determined by what someone is willing to pay but value isn't. If the value from art comes from expression, then LLMs directly attack the core value of art.
Damien Hirst, among many other prominent modern and historical artists, famously employed teams of human assistants to execute the bulk of the work. In the Hirst case that extended to the spot paintings, many of which he had very limited involvement in as a direct feature of the concept of the work itself.
Something tells me that doesn't alter the value of the art as expression of the intention of the artist, and not the assistant be it human or machine. In the spot painting case he was deliberately playing with this idea to the degree it added to the perceived value.
LLMs don't impede human expression.