Shadchanim can charge what they want, when they want and how often they want. You are free to use the services of someone else.
(If you have an issue with shadchanim, I imagine you also have an issue with yeshivos and seminaries who charge an application fee, a registration fee and then tuition. Leave this discussion to another thread).
I am NOT a shadchan (not in the professional sense anyway) and dont know any professional shadchanim, but I would imagine the $150 (or whatever they charge) for the “initial consultation” is to weed out those who are serious from those who are looking to throw as much as they can against the wall in the hope that something sticks.