I've noticed when I go to a chiropractor that has an adjuster they tend to "sell" their package like that. It is the "new" marketing technique to pay for their equipment. I was office manager (temp) for a cp and that's how their health care was to be "sold".
When I go to a regular cp, a "hands-on", I've been told to come back when I feel like I need another adjustment, not usually more than once a week.
I got caught up in this a couple of years ago and ended up paying about $1,000 over the course of 3 months. I felt better while being treated, but the problem came back.
After that expensive course, I went to a regular cp, did the hands thing, felt better, but paid $100 a month.
I still have the problem and go occasionally, but cp only fixes the symptoms, (in my case)