I used to go to a CDC who charged a reg fee but she also gave me a free shaker cup and stuff in a starter pack so that was why she charged it. But my current CDC did not charge. And I pay £2 / brick or bar and £1.80 for soups or shakes.
However the prices do depend on the CDC and I recommend you shop around to find the cheapest one. I, for example, inquired re prices to all the CDCs in my area and decided to go with mine because of location and convenience, although she is not the cheapest around. I would reccomend you do the same as, even if you find a cheaper CDC but it's out of your way, you are less likely keep up your appointments with them.
Hope that helps?