As someone that was in college in 1997, I think that estimate is way low. I bought ~4 CDs per month and so did most of the people I knew. You're forgetting that we traded and sold back discs, and that music was more actively discovered. If you cared about finding music, you'd find local deals and make connections that could stretch a dollar, and most young folks budgeted much more than $10/month. You heard about bands from magazines, friends, a mention in an artist interview, etc, and it was not uncommon to buy more randomly. Hell, I've bought albums simply because the cover looked cool and it was in the right genre.
My point is that music discovery, like all recommendation systems right now, is severely lacking in what made media discovery more meaningful in the 90s - that controlled chaos that led to surprises. Now everything collapses towards the mean of mediocrity. Sure you discover more 'bands' now, but they're belting out the same tracks with an extra half beat or a pitch shift, so I hardly call it 'discovery'. Long-tail used to be more fringe, but high-quality and related, unlike now, where it's the worst within the technical bounds of the algorithm. We're discovering more within our local minima, which is technically discovering more, but in the most frightfully boring way possible.
I would not have been exposed to at least half of the music I regularly listen to now if I had something like Spotify back then. I tried to use Spotify, Pandora, and Google Music, but after a month they each felt like I was listening to generic music station #342398 and I went back to purchasing albums. It's weird when a single album can be more diverse than a station with nearly limitless tracks to pull from.
And don't even get me started on how recommendation services have killed the idea of an 'album' - maybe the most rewarding facet of music production basically wiped out in less than a decade.