If we take the general situation (as the one you've described) - i personally believe it's okay. I used the following service - http://essaytools.com/ - when i was a student. If to be honest, used it for assignments on subjects i really hated or didn't see any sense studying. BUT! i've never handled in the papers they did for me. Yes, they were good, really good (about 25% and less plagiarism which is okay), but i paid for giving me ideas and used those papers as the source of ideas for my own work.