> 100,000 albums being released every year, which means in our lifetime we'll hit 1 billion+

Even assuming a lifetime is 100 years, that would be only 10 million albums. There would have to be 10 million albums released per year to get to a billion in a lifetime.

I think a lot of albums don't take much effort to produce, EPs from garage bands and bedroom turntablists probably require less effort than even a trashy novel. Of course a decent number of those 300,000 new books are very low-effort affairs as well.