@jmopp I don't mind the occasional ad in between songs, but only if it's a single add, occasionally, not between every single song (like maybe once every five songs or so). But I'd draw the line at *interrupting* songs in the middle to play ads.
I pay for Spotify because the free version isn't supported by my Google Home, and I like to be able to say, "Hey Google, play xxx from Spotify" or even just, "Hey Google, play some music."
I don't pay for YouTube because I'm used to ad breaks in videos. It's a well established thing and it doesn't bother me. Although sometimes, it can get a bit much.
But yeah, cost is also an issue. If I found the service really useful and it was €1 per year, I might just pay.
In general, I'm a freeloader. :-)