Evaluation of education credentials

I am studying Mechanical Engg (undergrad) from the University of Mumbai. I applied to Carnegie Melon's MII-PS program, and they want evaluated transcripts, and GPA converted to 4.0 scale. Mumbai University uses the % scale. CMU recommends WES's $160 course by course evaluation, but other options that provide an official evaluation of course work and my grades are also acceptable. Are there any other cheap alternatives to do this?