Although it's focused on a more 'elite' audience and companies that use literary fiction to make themselves look more classy and cultured, rather than on the mass marketing you're thinking about, it's definitely an example of writers as marketable commodities. I thought it was fascinating.
I love thinking about stuff like this, thanks for writing!
Did you see this New York Times article? It reminded me of what you're writing about here:
https://www.nytimes.com/2022/04/18/t-magazine/book-stylists-instagram-influencers.html (subscription might be needed, I read it through the library's online service myself)
Although it's focused on a more 'elite' audience and companies that use literary fiction to make themselves look more classy and cultured, rather than on the mass marketing you're thinking about, it's definitely an example of writers as marketable commodities. I thought it was fascinating.
I love thinking about stuff like this, thanks for writing!