Economic Justification / Rationale for MPLS

Ladies and Gentlemen: I have been conducting research looking for the economic justification for MPLS. I have some feedback, but sound rationale from the industry has eluded me thus far. I am looking for a paper, website, etc that explains the benefits of implementing MPLS (other than technical) or gives some economic modeling for MPLS-based networks. Any help, reasoning, rationale or personal insights/views would be greatly appreciated. Thanks in advance, Shannon M. Lake Sr.