In my experience, I have not seen any commercial success come from paying someone to publish your songs. Notwithstanding the discussion about Sing Song Agreements, publishing is not generally about an individual song but rather a relationship where both parties share in the risk and reward. In these scenarios, you end up, at best, with a demo recording or a lead sheet prepared by that “publisher.” At worst, you transfer ownership of your song and pay hundreds or thousands of dollars without any serious return. A “publisher” who requires a payment to “publish” is bearing no risk in your song and is not likely investing in your relationship.
Excerpt from "The Songwriter/SPublisher Relationship" by Don Cason, found in The AGMA Music Curriculum - Tools for Ministry and Career (1999, GMA, out of print).