The cost is too good to be true. It is only human to try to find the best service at an affordable price. However it is also true that you get what you pay for. If a service says that it can write your resume for a few dollars it is better to be cautious. Creating good quality resumes requires using specific skills. The cost can be lower only if the summary of your career is part of a mass produced set of similar documents.
Functional format is best for those who are switching their career or have large employment gaps on their resume. In this format, you dont have to list the joining or resigning dates of the previous employments. Functional format will hide your employment gaps or your job switching.
Ask yourself - is a cheap resume of any worth if all it does is extending the period of your job search? The answer is simple - no. The cost should not be the sole focus when you choose a resume writing service. The priority should be on the quality of the final product. Only a unique resume that captures the attention of prospective employers and guarantees an interview call is worth your money.