How many different restaurants do you patronize? In my household the number is in double digits ranging from fast foods to fine dining.
Now suppose a bare majority of the eateries in your town forces all the others into a dues-imposing restaurant association that fixes prices, hours and terms of service for all of them.
In this example, it is illegal for customers to negotiate with a restaurant without first going through the association. Moreover, all new restaurants must join the association, pay its dues and abide by its rules.
Economists call such an arrangement a cartel. The industry is monopolized by its trade association. Some members and the organizers are better off; customers and those members who do not wish to be subject to the cartel’s control are worse off.