I listen to a lot of underground music (namely black metal, hip-hop, and the like), and not only are CD's selling out regularly, so are cassettes. Once they've sold out, they hit Discogs and Ebay at severe markups that people are happy to pay. Several CD's that I've bought in the past few years have compounded many times over in value, as the supply can be very limited but the demand isn't diminishing. The spread on my collection per Discogs ranges from $800-$2500. That lower bound has been continuous, but I saw the upper bound increase by $1000 in just the past two years.
It's also not uncommon for me to go hunting for CD's that originally sold in the 80/90/00's, so as to get around "re-masters" that undo the lo-fi sound underground music fans enjoy so much. I doubt my copy of The Cramps' first compilation* is going to reflect in last year's CD sales.
I'm aware that this is a niche interest, but it's a growing niche. There are a few subreddits that I've followed in the past (/r/CDCollectors and /r/CDKvlt), and in my time there, I saw those groups grow considerably.
There IS a CD Revival, if you look in the right place.