I have my NAS on a private VPN running on my own server. The NAS have my music (roughly 2/3 from physical media, 1/3 from various DRM-free source). I use it with a simple mobile app (CloudBeat) that can work in both online and offline mode where you can download what you want ahead of time by ticking a checkbox.

It doesn’t cost much: the VPN server do other stuff and is cheap to begin with, the NAS have some maintenance cost for storage, but that’s like a drive every two years top, content never change of disappear, it doesn’t slurp my bandwidth constantly, etc.

Even factoring the cost of a separate backup, since the whole setup store a bunch of other stuff and services, it’s probably more cost efficient too, if you don’t consider the initial setup cost.

And if needed, I can “lift” some content from streaming services too and put them there.

The only reason paying for a streaming service still exist is convenience, at the cost of bending over whatever craziness they come up with.