If the music was high quality and interesting to me on its own, then I would consider buying. However, it would need to be reasonably priced and high quality.

I will --- on rare occasions --- purchase ancillary material from games. When the music is amazing I have no problem getting a separate sound track. For the artwork and story, when the visuals are amazing I am sometimes willing to pay a little extra to get the collection of artwork building up to the final products, since often the sketches are quite beautiful. (On several projects I picked up my own collection of original sketches, after the artists put together several hundred sheets of characters in experimental poses.)

Keep in mind that the purchase is competing with all the other stuff out there for my entertainment dollars. It needs to be high quality.

The more diverse the offer, likely, the more difficult it is to sell it, I would say.

I mean, if you offer music AND art AND story, I pay for all of them. To make it worth the money, I must like them all, or I would buy only one thing that I like for a very high price.