It depends.
There has been a fair amount of criticism of Spotify from various artists (summary
here).
If an artist is signed to a recording label, spotify payments are paid to the label, not direct to the artist, and they appear to take their own cut (or more). That wouldn't be the case with unrepresented artists, though you could probably check their standard terms for what they are paid.
70% of Spotify revenue is claimed to be paid out in artist royalties, so about $8.40 of your subscription is going to the people you listen to (or their agents/hangers on/managers/rent seekers).
Deals for CD sales isn't always much good either, though.