A producer is entitled to whatever was agreed to by the talent. Often a producer is paid out of royalties earned by the talent. Sometimes its a flat fee, like for a demo. More likely it is a percent of the talent's overall earnings from royalties, sales, performaces etc. If there is no agreement, the producer could still have a valid claim against the talent for a fee that represents what it cost the producer to produce the recording.
This response is intended as general information only and does not constitute as legal advice or form any attorney/client relationship