It seems like there's a pretty easy solution to this problem, but maybe I'm missing some key info, since I'm looking at it from the outside..
1) Don't allow uploads from any account less than a week old.
2) Anyone caught uploading an Ai track has their account warned on the first offense, banned for the second one. This incudes any payment details they gave to collect money for their garbage.
3) Cut the number of uploads an account can make to what a human artist could "reasonably" produce in a week. I leave it to the musicians at Deezer to determine that number. Make it a growing scale based on account age. The newer you are, the fewer tracks you can upload.
This should make it just hard enough to keep setting up new accounts, that the minimal amount they stand to make from trying won't be worth it. It won't be 100% but it seems like it would cut down enormously on the amount.