Adding belts to the rank structure to increases profits seems to be a common occurrence in the martial arts industry; but charging for belt stripes does seem excessive; I do not think this is an industry standard. If the services offered by your school and the costs for those services are in line with those of other schools in your area, then you have nothing to complain about. No matter, the amount of fees charged by a school, these fees should be disclosed to potential students and may be grounds for voiding a school contract. With some searching, you can always find non-profit or part-time for-profit schools where the quality of instruction is just as good, if not better, than that found in full-time for-profit schools.
If you are displeased with the school and did not sign a contract, find another school. If you signed a contract, read it carefully to see what options you may have. You may choose to suck it up and take advantage of all the services until the contract ends, and then change schools. You could just train without testing; however, the way school curriculums and rank systems are set up, if you do not test for and advance in rank, you will not be taught new things and will just train in the same thing for the remainder of the contract. At worst, you can always cancel the contact and pay whatever amount you agree to pay for cancelation, and then find a new school.