The net reminds me of the wild, wild west before the lawmen came. There's lots of scams and rip-offs. Anyone can declare themselves a professional. Be aware that legitimate agents, producers and production companies DO NOT charge a reading fee. My advice is to spend some time on a site and see if you feel you can benefit from that person's evaluation.
Most people can tell intuitively if a person walks the talk.
It's my position that a professional evaluation should include running margin notes of what's happening to the reader as the screenplay unfolds. This is real information you can use in evaluating how the script works. Your script format should be corrected. Some critiques will include general marketing suggestions which can be quite helpful. So, if you're unsure if you should be marketing your screenplay then seek out a professional for some feedback.